That Time I Got Isekai'd Again and Befriended a SlimeTanJaded

Summary :

Confirmed. Unique Skill: Formulaic Casting successfully acquired. Notice: Current body of Tanya von Degurechaff exhibits traits of physical, mental, and spiritual damage. Constructing body… cleansing mental corruption… preserving soul…

Chapter 1: A Young Girl's Second Reincarnation

The end is not the end. When Gods and pesky, stubborn mortals are involved, there's always another path. For Tanya, this means reincarnation... wait, haven't we done that already? Well, I guess that makes this that time Tanya got reincarnated into another world. Again.

Notes:

And then I said I'd wait until I finished my other fanfics and writing projects, you know, like a liar. Youjo Senki and Tensura are two of my favorite anime/manga/LN series. So naturally I wanted to write a crossover fic featuring both of them. I could have technically wrote an Isekai Quartet fanfic to the same end, but I honestly don't care about ReZero or Overlord, and while Shield Hero is cool, I never finished it.

Enjoy!

(See the end of the chapter for more notes.)

Chapter Text

I've always had a... distaste, for concepts of fate, or the divine. Of some higher power in the universe (or multiverse, I suppose), influencing and interfering in affairs not their own. Fate is fluid, and the wheel of destiny operates on human hands.

Humans have free will.  No one can take that away from us. We are able to use the cards we are given to obtain the future we desire.

Then, in a fair world, it is further our right to stack the deck in our favor, through applications of logic, reason, and rationality. Such is the advantage of being separate from beasts.

But this world, and every other, is not fair.

-=-

Unknown Time

Unknown Space

Unknown Location

Light. A bright, holy light surrounded her on all sides. A feeling best described as ethereal in nature flowed through her body.

And as a rational being with an avid disgust for elements of the divine, Tanya found herself repulsed.

Even through closed eyelids, the light was almost blinding. Not the most comforting experience, all things considered.

-=-

Art by Me (@tanjaded)

-=-

So, is this death, then? Last time went a bit…

Differently, she recalled. For one thing there wasn't some irritating Devil claiming to be God greeting, or rather berating, her.

Being X, you bastard. Of all the times, now you decide silence is appropriate? Take responsibility for your actions!

It was silent for a moment.

Jeez, at least give me some sort of deity to talk to at this point. I need someone to rant at.

Confirmed. Extra Skill: Voice of the World Communication… successfully acquired.

Fuck. This wasn't supposed to happen. How did I even... ah, right. Mary Sue. That self-righteous bitch. Did she get the best of me? How did I even die?

It must have been something extremely powerful. Maybe Being X had finally pulled up his bootstraps and decided to off her himself. Or perhaps he'd blessed Mary Sue again? That seemed like something he'd do, doubling down on his idiocy rather than admitting defeat like any sane or rational being would.

I guess I wasn't strong enough? Ah, I think the Type 95's mental corruption is really starting to get to me. I can't quite recall. If Being X were here right now, there's no doubt Tanya would have attempted to strangle him. Damn it all. If I didn't have to rely on the Type 95 everytime things went south, this mental corruption BS would practically be a nonissue.

Notice: Semidivine relic Elenium Type 95 computation orb nonexistent. Removal of reliance on relic impossible. Constructing adequate substitution… Confirmed. Unique Skill: Tetrabattery Limit Enhancement… successfully acquired.

…It's a shame though. Just one more push, just a few more weeks, and the war would finally be over. I was so close. We were so close. Heh. To think, I actually had people I could call friends this time around. Subordinates that changed for the better, comrades-in-arms that I've spent years with…

She mentally shook her head.

I never even got to share a friendly alcoholic drink with them. That would have occurred soon too now that I think about it. Finally 18 years old in this second life, and able to drink by Imperial law. Well, all that's down the drain now. No use crying over spilled milk, or alcohol in this case.

Tanya sighed internally.

Formulae-based magic was nice too. Magic in fiction is usually so random and irrational, so reincarnating in a world where you could perform it with understandable and ultimately reasonable calculations was at least a small consolation for my shitty situation. I certainly liked flying around under my own power. When I wasn't being shot at, of course. It was nice. Even fun, on occasion. Damnit all. Just when things were finally looking up… honestly, I wouldn't have minded staying like that.

Silence met her.

… Ah. it's really not fair, you know? Not at all. What else was I supposed to do? What even was the point of all that struggle? Just for this? I'm only human, after all.

That was the last thought Tanya had in her second world.

Confirmed. Unique Skill: Formulaic Casting… successfully acquired.

Notice: Current body of Tanya von Degurechaff exhibits traits of physical, mental, and spiritual damage.

Constructing the same body… Failed.

Constructing a similar body without damage… Successful.

Cleansing of detected accumulation of mental corruption… Successful.

Preservation of soul and memories… Successful.

-=-=-=-

Tanya came back to consciousness with a start.

Ah, am I going crazy? I knew the mental corruption was getting worse, but this is a bit ridiculous. If I've developed schizophrenia, could it at least stay away until after I've finished dying?

Tanya let out a huff of irritation.

 I'm sure Mary Sue would find that hilarious. Me, her hated enemy, going crazy right before dying. She might even call it a sort of cosmic justice. As cosmic joke is more like it. That might be the worst part of this whole situation, my death giving her validation for that ridiculous belief she has in that devil.

Though, as bad as this was, it might be a bit easier to handle if Tanya knew exactly how she died this time around.

...How did she even kill me?

All she could really remember was a bright light, and Mary Sue's glowing face. As in the literal sense of the word, indicating mana usage.

Well, she also vaguely remembered the Type 95 going haywire… uh, even more haywire than one would normally expect.

Actually, the light from then was not unlike the one she had previously been floating in. And actually, now that she thought about it further, that holy light or whatever had been gone for a while now.

Tanya twitched her fingers. Her brow furrowed, as a different form of light bled through her still closed eyelids.

Uh, wait. Did she even kill me? I can still move my body. That doesn't seem very dead to me.

She did a mental tally, moving each finger, then each toe one after the other. Then, she clenched and unclenched her hands. She rolled her shoulders. She tilted her head from side to side. She-

Am I just lying on the ground? Tanya thought incredulously. Weiss is never gonna let me live this down.

The Argent sat up and opened her eyes. Then immediately closed them again, as the morning sunlight attempted to gouge out them out with its intensity.

Okay, I could have handled that better. You're still in a warzone, Tanya. Let's do this logically and not waste any more time.

Tanya opened her eyes slowly this time, letting them adjust gradually to the sun's unforgiving rays. It was as her vision adjusted that a few things became readily apparent.

The most obvious was the weather, closely followed by the location. It was a sunny and warm morning, not a cloud in the sky. A forest clearing surrounded her, lush green grass and well-sized trees propagating outwards from the crater she was sitting in. Nothing too out of the ordinary.

Except, Tanya had been fighting in the cloudy skies over the Russy Federation. In the evening. During winter. Over a frozen, treeless grassland.

"What the hell…?" Tanya murmured, gingerly getting to her feet.

She made to step out of the (was it an impact crater?) pit she'd been lying in, but just as she was doing so her sense of balance shifted. She nearly ended up right back on her ass, barely managing to stabilize herself.

Tanya stumbled as she attempted another step, her legs and arms doing more harm than good in her impromptu balancing act. Unfortunately, it seemed she wouldn't be selling tickets to the act anytime soon, but after just a few minutes of struggle, she did manage to stop nearly falling over.

"What in the- the hell is going on?!" The increasingly confused Colonel kept as still as possible, internally lamenting her randomly shit sense of balance.

When her balance seemed to have settled a bit more, Tanya quickly did a once over, scanning herself for any sign or indicator as to why it was being such an uncooperative bitch.

She blinked. Well, a few things came to mind right off the bat.

Her clothes were the same as when she'd… well, is "died" even accurate now? Regardless, she still had on her mage flight suit, along with her harness and its various pouches. However, her backpack was missing, as were all the other supplies she usually carried in the aforementioned pouches.

Her weapons were gone as well, with both her submachine gun and her Luger along with her main, backup, and backup backup knives missing from their respective holsters.

This also was the case for the Type 97 and the cursed Type 95. Which meant, for the first time since her original deployment to the Rhine Front, she was entirely without a multicore computation orb.

It was mildly concerning, to say the least.

Though, for some reason her goggles had remained despite her helmet mysteriously being gone. No wonder her head felt so light.

So, it seemed all she had on her were her clothes. And discounting the dirt from her apparent nap on the ground, everything was spotless. Like brand-new, in fact. Her black gloves and her boots felt like they did first time she'd ever put them on.

Somehow, she'd become like the mage equivalent of new car smell.

Yet, that wasn't even the most immediately noticeable change.

Whoa, is the ground farther away? Tanya did a double take. She patted her torso idly. I feel different, too. My body feels… stronger, for lack of a better description. And my mind feels clearer than it has in years. Was the Type 95's mental corruption that bad? It's like I just got sober after years of being constantly near drunk.

The Argent brought her hand up to her face, balling it into a fist then relaxing it, turning it back and over and back again.

I feel great. Better than great. What happened to me? Actually, I can tell that my body and mind aren't the only things that have improved. Perhaps it's more accurate to say my entire being has improved. Or maybe "fixed" is a more accurate term. I'll have to do some tests to make sure. Either way, this can't be the work of Being X. No chance in hell that bastard would do something to actively improve my life.

"I can't say I mind getting away from the warzone, but this is a bit ridiculous." Tanya said aloud, more to confirm she was actually awake than to be heard by anyone.

Speaking thoughts was a good way to ground oneself through physical sound. That was just basic psychology.

...Was it? She'd only taken one or two psychology courses in college, and that was two worlds ago. 

Ah, nevermind.

Right. So what happened to her? As of right now, she had two working theories.

The first theory was that she had actually died, and this was the afterlife. Not ideal by any means, but she certainly could have found herself somewhere worse. Like Hell, for instance. Or with Being X, which would also be Hell, just not in the literal sense.

Still, to have died and reached the after life so easily was a basically a slap in the face after her years of conflict against Being X. The very thought made her blood boil.

Now, the second theory was that she had time travelled. As outlandish as it sounded, it would explain both her apparent increase in height and the overall improvement of her being.

The former could be explained by her aging with the time transition, and the latter by an extended period of time away from the Type 95 and Being X. Whether it could be considered more of a "Rip Van Winkle" scenario, or a "Hot Tub Time Machine" scenario was currently unknown.

And in terms of outlandishness, she'd literally been reincarnated into a war-loving world by a vengeful deity-like being with productivity issues. Time travel was practically reasonable when you knew that much.

Tanya rolled up the sleeve of her left arm, noting the presence of one of the small scars from Anson Sue's kamikaze attempt all those years ago. She checked the other arm just to be sure. Again, and exactly as she remembered them, were some of the various marks and nicks she'd accumulated over years of conflict. 

Would I still have these in the afterlife? Conversely, wouldn't they have faded more if I'd time travelled?

She wasn't getting anywhere with this.

"Alright, first things first: recon."

It was lucky, though she did so abhor assigning such an unreasonable variable as luck to any scenario that could be reasonably explained, that her lack of computation orbs would be a non-issue for this.

Interestingly enough, the majority of magic was inaccessible to lower-level mages without the use of a computation orb. This included flight, mid to high level piercing, optical, and explosions spells, along with basically anything that required more than a small amount of mana to maintain.

Part of this was due to magic's relative infancy as a subject of study, and part of it was because channeling mana through an inanimate object made it less likely to overload and destroy, say, your hand. 

There was a reason guns were so useful in spell casting.

In any case, the phrasing is also important here. The point of reference being "lower-level mages".

Tanya was definitely not a lower-level mage. She'd long since mastered the use of minor illusions, physical reinforcement and enhancement, and low level optical and piercing spells without the assistance of a computation orb.

Once, she'd even blown a tree stump from the ground using an orb-less explosion spell, though she refrained from doing so again due to the danger and finnicky nature of explosion spells in general. It wouldn't do her any good to lose her fingers the same way a hillbilly with a fireworks kink would.

Even so, she knew the usefulness of casting formulae without an orb, regardless of the danger. In her opinion, relying entirely on potentially faulty equipment was the epitome of irrationality.

That wasn't her. If her orb malfunctioned in any way, she certainly wouldn't be helpless. 

That being said, another great reason for learning orb-less magic was its inability to be detected. Generally, mana detectors were unable to detect mana usage below a certain level. This base level was higher than most thought could be generated without an orb.

Yes, considering exactly how skilled Tanya and her 203rd were with mana, this was an oversight. But the understanding of mana and magical systems were still relatively unexplored, so for now it was an allowable oversight.

All of this was a nice, roundabout way of explaining that orb-less magic was extremely useful for stealth reconnaissance. Oftentimes enemy mages and their bases were detected, ironically enough, due to their own usage of detection and scanning spells.

That's how Tanya had discovered and destroyed that one base of operations in the Entente Alliance being ran by Albish intelligence officers.

Thus, for the sake of stealthy reconnaissance, Tanya decided to activate a wide range mana detection spell without the use of her computation orb.

Of course, the real reason she did this was because she didn't even have her computation orbs on her, but the explanation regarding stealthy reconnaissance sounded much more professional than "Ah, I didn't have an orb on me".

Properly justifying your actions is a necessary skill in war. A skill which she happened to excel at.

Tanya flared her mana without hesitation, activating the spell.

...Then immediately let it go, clutching at her head all the while.

"Ow ow ow…" Well, it had worked. That much was certain. The problem was-

There's mana everywhere!

And then, the icing on the cake.

Formulaic Casting Subskills "Mana Detection" and "Mana Aura" detected. Combining and upgrading to Extra Skill: Magic Sense…

Confirmed. Extra Skill: Magic Sense… successfully acquired.

The voice echoed in her head, even and emotionless. And also, fairly agender, though leaning ever so slightly male.

Tanya straightened back up, the pain from her spell's feedback fading. 

Her stomach sank, a third theory presenting itself.

She just might have reincarnated again. In other words, she'd gotten isekai'd.

For the Second. Fucking. Time.

And, as a blue haired man with a large, upturned horn on his forehead stepped out from tree line, this theory became even more likely.

...Then, it became practically fact, as a taller man with spiky red hair and two black, upturned horns stepped from the trees as well. Also, his hand was on fire, and he did not seem at all concerned about it.

The purple haired woman with the massive sword and, you guessed it, an upturned horn, was just salt on the wound at this point.

Okay, stay calm. I'm in another world. I'll think more about the implications of that later. Right now, I'm more concerned about the…

Tanya tilted her head.

Hm, I'm not sure what they are, actually. They're humanoid, but as far as I'm aware, humans don't have horns. Not the ones I've met at least. Then again, you never know with fantasy.

"What is your business here, human?" The red one spoke, pointing his flaming hand at her in a manner that would be threatening to most. 

"Human"? Ah, nevermind. Thanks for confirming my suspicions. 

Tanya raised her hands slightly.

Look at me, I'm unarmed. You wouldn't attack a helpless person, would you? Show some concern for human life- ah, actually, does the concept of humanitarianism even exist among non-human humanoids?

"Ah, before that, would you mind telling me where I am?" Tanya looked around, before shrugging apologetically. "You see, I'm finding myself a bit lost here."

Lost in both the literal sense and in a mental one. Seriously, the hell is going on here? 

"I find that hard to believe." The purple haired woman said, brandishing her sword. 

It was almost as long as the woman was tall, and she wielded it with ease. This fact unnerved Tanya way more than the guy who could control fire.

After all, she could do the fire thing too. She wasn't impressed. The massive sword though, that was impressive. And very concerning.

Okay, so maybe I'm trespassing somehow if just speaking provokes that sort of reaction. Or that's just her personality. She's clearly not the most reasonable of the bunch.

"No, really. I'm telling the truth."

Tanya wondered if telling the truth would even help here. Red and Purple, as she had mentally dubbed them, seemed somewhat inclined to violence, but the blue one was merely leaning against a tree and observing her.

"I was in a battle before I got here. The last thing I remember was a flash of light, then I arrived at this spot. I'm not sure how I got here, or even where here is. Nor do I know how you found me so fast."

An intentional use of words there, secretly inviting her potential foes to explain valuable information. Any advantage was a welcome one.

"We detected two large magical auras using Magic Sense. The larger of which being in this area." Blue finally spoke.

Gotcha. So, they detected me with Magic Sense. Don't I have that? What was it that voice said? Something something my mana detecting spell and my mana aura melded and became "Magic Sense". And it's apparently been upgraded too. This is... just like an RPG game from my first world.

"As Great Rimuru's sworn subordinates, it's our duty to protect Great Rimuru and the Jura Forest Alliance from potential threats." Purple pointed her sword at Tanya. "Like you, stranger girl."

I'll allow that. Hm, this "Jura Forest Alliance" sounds important, and these guys are clearly big fans of this Great Rimuru person. Maybe now's the time to try out this "Magic Sense" skill. I should know what I'm dealing with just in case thus gets violent.

"Ah, threat? I'm not sure what you mean. I'm just a lost-" Soldier? Absolutely not. Traveler probably wouldn't fly either. Well, this does seem more like a fantasy world than her old one, so how about, "-mage. I assure you I mean no harm."

So, how exactly do I… ah, there we go. Just keep the output low and-

Tanya's newly acquired Magic Sense spread over the immediate area. It was odd. She could still see with her eyes, but it was like a new field of view had been juxtaposed on top and beside it.

It was sort of what she imagined being able to see into a fourth dimension would be like.

Tch. They're all extremely powerful. I think. I'm not sure what the spectrum of magical strength in this world is, so I can't exactly compare their level of strength against mine. What I can tell is they all have a lot of mana in reserve. The red one especially.

Without warning, Blue tensed up. Red and Purple saw this at the time as Tanya did, and tensed up as well in response.

Tanya's eyes widened.

He noticed Magic Sense? Suddenly, she remembered what he had said earlier. "Detected a large magical aura"? He must mean me. Does that mean I'm broadcasting?

She focused Magic Sense on herself for a moment.

Shit, I am broadcasting! How… right, this is a different world; mana and magical systems must interact differently here. This would never have been an issue in the other world. I feel like I've been walking with my fly down! Maybe if I just reel it in…

Tanya closed her eyes and breathed deeply, concentrating on the feeling of her mana. Now that she could see it, the way it was wildly fluctuated outside her body without any sort of willful intent almost shocked her.

Yeah, she could see why they might have felt threatened. A moment later, her mana drew back into her body, the intent to suppress her outward aura being all it took to reign it in.

The two-time reincarnate sighed in relief.

Right, now that we've solved that problem, let's deal with another. Tanya opened her eyes.

Just in time to see the massive sword swinging down to cleave her in two.

CRASH

Magical and metal-related sparks flew everywhere. Tanya deflected the strike with a mage blade covered arm, narrowly avoiding yet another death. Her arm stung from the effort, her instinctive reinforcement spell working overtime just to keep her intact.

Don't attack people out of the blue, lady! What kind of idiot just does that?

Even with her arm and magic taking some of the force, the ground to her left cracked and split from the deflected blow.

Yeah, these guys definitely aren't human! This strength is monstrous!

-=-=-=-

A Few Minutes Earlier, Late Morning

Grand Home of our Lord, the Great Rimuru (Rigurd, I told you not to call it that!)

Jura Tempest Alliance

"Hm?" Rimuru looks up. In front of him, a diary sits open on his desk, the pages completely blank.

Notice: Two similar magical auras of great proportion have just appeared within close distance to the city.

Yeah, that's what I thought I felt. Do you think it's a threat?

Answer: Threat level unknown. The simultaneous appearance of two similar magical auras close to the city heavily increases the chance of a threat.

If they wanted to attack though, why would they reveal themselves outside of the city?

Answer: Inconclusive.

Yeah, that helps. Rimuru thinks sarcastically, then shrugs. Well, I'll go check it out. We'll head to the larger one first. Let's hope they're willing to talk, whoever they are.

~OPENING: NEW BEGINNINGS ARC~

-=-=-=-=-=-

Known Skills List

Tanya:

Extra Skill: Magic Sense

Extra Skill: Magic Aura

Extra Skill: Voice of the World Communication

Unique Skill: Formulaic Casting

Unique Skill: Tetrabattery Limit Enhancement

Notes:

Fyi "OPENING" links to a song for the arc's OP. Because that's a thing I decided to do

Tanya's "death" will be explained. Eventually. Also, the Skills list will only include Tanya's Skills along with one other character (I'm sure you can guess who), so don't worry about it getting too unnecessarily complicated.

Thanks for Reading!