Chapter 3

The passage of time is swifter than you prefer it to be, and it isn't long before you've spent two whole weeks at Butterfly Mansion. Each day follows the same routine – waking before dawn, enjoying a quick breakfast courtesy of either Aoi or the estate's Kakushi, then doing research until it comes time for dinner – albeit with minor deviations as you settle into the rhythm of living with strangers.

A large chunk of your research time sees you spending hours in the laboratory pouring over the notebooks Shinobu handed over, and you discover early into your reading warpath how much you've been underestimating the Demon Slayer Corps.

You always found it impressive how an organization as large as this has survived the passing of eras and remained prolific, eluding the government despite its activities literally spanning the country. It never crosses your mind to seek out the reasons behind its success, your rank and duties being what occupies your attention majority of the time, but it's different now that an entire wealth of information has been willingly dropped into your lap.

Knowledge and the ability to execute on it. You identify these as key factors which have ensured the Demon Slayer Corps' continued survival.

Handwritten annals from decades past, topographical maps, detailed accounts of natural disasters and demon attacks from long gone villages, towns and cities from the ancient era up to the current year… you are confident this information cannot be found anywhere else. Even notes on innocuous subjects like agriculture and fine arts have been hoarded like gold.

Just how deeply do roots of the Ubuyashiki Family run for them to have this much information casually sitting around? All the books and notes used in your research would have cost nothing less than half of the country's treasury should you have sought them by yourself. If the books and notes Shinobu has on hand is capable of putting national scholar libraries to shame, you can't begin to fathom the scale of information which Oyakata-sama houses back at headquarters.

By the time you wrap up your research to start on your assigned tasks, your doubts on whether is it possible to live up to the expectations placed on you are completely forgotten. With the knowledge gathered at your fingertips, even if you'd been underqualified, you think it would've been impossible to fail.

It also helps that Shinobu's words had not been lip service. Combining your experience in trade and the fruits of your research, you manage to produce fairly remarkable results in a short span of time.

You dig out all manner of flaws from the plans given by Shinobu and Oyakata-sama. The transport logistics of medical supplies are rewritten to accommodate your new insights, while existing trade under the Ubuyashiki family see a number of marked improvements. The use of water-faring modes of transport will make transport of goods more efficient, and by successfully renegotiating existing deals, the businesses are set to turn better profits.

Your workaholism also ends up rewarding you. The organization's previously stalled trade plans you had dusted off and rewritten in your spare time were spirited away to be looked over. According to the kakushi who reported back to you, those end up being accepted as well, though they won't be implemented until more manpower is secured.

It comes as no surprise your efforts will be rewarded. You didn't work like a man possessed for monetary benefit, but you won't turn down recognition for your success. It will help ensure you're less hated among fellow slayers, especially the ones who think you just a coward or greedy merchant.

You convey your lack of desire for a tangible reward to Oyakata-sama, but as compensation for not receiving a tangible reward, you are given permanent access to the notes and tomes you've read thus far. You are also allowed to request for copies of books from the Demon Slayer Corps' main library. Though you can't take any of these things out of the Butterfly Estate, this favour granted to you is almost too ridiculous to comprehend.

This is something not even the riches of an Emperor can acquire. Knowledge is power, and it can be seen how much Oyakata-sama trusts you to allow such a thing. Your loyalty to the Demon Slayer Corps has never been shaky, but this act of faith ensures if there ever comes a day where Ubuyashiki Kagaya is in danger, you will gladly give up your life if it means protecting him.

And years later, when reflecting on your achievements from the period where the threat of Muzan still loomed, you will find yourself laughing at your past self for the assumptions he made. Ubuyashiki's favour and the authority to access an endless supply knowledge is well and fantastic, but compared to what you end up gaining from your time at Butterfly Mansion, those things are simply incomparable.

---

You look up at the sound of the door sliding open. Shinobu glides across the lab dressed in her usual Pillar garb, looking fresh as a daisy despite returning from a mission a little over ten hours ago. The stampede of feet had woken you up this morning, and you'd gone back to sleep after confirming it was simply Aoi and the rest who'd been rushing about.

Their enthusiasm is understandable, though. Shinobu has been gone for slightly over two days, but you were starting to feel antsy. It is remarkable how much you have gotten used to her presence that you're more used to her being present than not.

"Good afternoon," Shinobu greets with her usual cheery air. "Are you surprised to see me?"

The 'Welcome back' on your tongue slithers back down your throat. Despite two weeks of peaceful co-existence, you refuse to let yourself be presumptuous.

"I heard the commotion last night," you reply. "It was of a delighted sort, so I assumed your mission went well. Was I right?"

"You certainly are. I only ran into a single demon. Disappointing, but then again, scouting missions are rarely exciting." Shinobu settles herself at her desk and starts to clear up the papers strewn across its broad surface. You assume the end to the short conversation and make to return to your work when she asks, "You're always busy working when I see you. Did you receive more work from Oyakata-sama?"

"I am doubtful this falls under that category." You look down at your journal. You had been sketching the concept of a throwable weapon inspired by several celebratory items you'd seen during the New Year. Your morning plan was to study up on the books Shinobu recommended, but it seems your listless mind had other plans. "Calling it a hobby might be more apt. It's something I do when I have free time."

"And what does your hobby entail?" Shinobu is looking at you now, curiosity dancing in her amethyst eyes.

"Nothing too exciting. Just jotting down any ideas so I can look at them when I get free time during a mission. You never know if something in here ends up as the final cog in an idea that makes me a fortune." This journal also doubles as your diary, not that you'd tell her. In your weaker moments, purging your thoughts onto paper has helped you immensely.

"You're quite the workaholic. You shouldn't work so hard, you know?" Shinobu sets down the gathered pile of papers at one corner, and starts dusting off the army of glass tubes and beacons she'd left there the last time she was here. "I heard people age faster if they put themselves under too much pressure. It would be terribly sad to lose an enterprising individual Oyakata-sama praised."

You can't help but laugh. When she shoots you a look of confusion, you gesture at your surroundings. "I do believe you've rubbed off on me. Practice what you preach, Shinobu-san."

"My," Shinobu shakes her head, wearing an exaggerated, wry smile. "I miss when you acted more reserved. You've grown cheeky enough to tease me, I see."

"It comes with practice," you say, looking away to feign arrogance. "I learnt that from you as well." Shinobu's refreshing laugh sweeps away your lethargy. You find yourself laughing along with her, buoyed by her casualness with you.

After your first day at Butterfly Mansion, bar the initial confusion caused by your poorly worded stance on life for a slayer, living with the insect pillar has gone surprisingly well. Research is a lonely endeavour, but because you work in the laboratory Shinobu herself frequently inhabits, you think you've spent more time with her than anyone else here. Working in such close proximity, it is inevitable that both of you would strike up conversations with each other.

As an added bonus to being on good terms with the person responsible for inventing poisons to counter Demons, you have received valuable insights in her field of study by way of discussions and first-hand accounts of her genius. Like the tomes of information she provided, Shinobu's companionship is also a reward in itself.

"A good student should seek to surpass their teacher," Shinobu says, smiling. "In this case it means you've done well, dear."

You ignore the rush of heat to your cheeks. "Why, thank you kindly."

One thing you're still unused to is Shinobu's flirtatious behaviour. You are thankful for your varied experience in sales and hiding of your true emotions, or your good relations with her would have soured long before you could get to this point. Aside from her fellow Pillars, you've noticed the reactions toward Shinobu are split between 'attracted' and 'fearful'. You understand their reasons, attractive people have a tendency to evoke the more primal parts of a human's behaviour, but it doesn't mean you wish to fall into the same trap.

Something that has helped you maintain your sense of sanity, however, is that your contact with her will likely be minimized once you receive your next mission. You're not a perssimist, but you're not so bold to assume Shinobu will let you continue to stay here now that your task for Oyakata-sama is deemed complete.

Your banter is interrupted when the cries of a familiar voice cut through the air.

"Mission! MI-SS-ION!" Your kasugai crow alights on the windowsill looking into the lab. It flaps its wings, its noisy caw resounding in the large room. "Go to Fukiya, FU-KI-YA! Demon sighted, demon SIGH-TED!"

And just like that, your peaceful days spent in Butterfly Mansion are no more. You anticipated this, but you hadn't thought it would be so… crushing. Emotions are such fickle creatures. Shrugging off your disappointment as best you can, you glance at the mess around you.

"You'll have to give me some time to clear everything here, Shinobu-san. I'm afraid I might have been too enthusiastic." You spy the corner occupied by bundles upon bundles of parchments filled with messy scrawls and diagrams and groan. You lower your voice, muttering, "How am I going to move my notes…?"

The prospect of dragging these bounded sheaths of paper to your house is not fun thought to entertain. The task itself is not hard or difficult beyond measure, just annoying. Truly, what you're dreading is returning to your empty house, probably dusty from misuse by now, and brimming with painful memories.

"Clear everything, you say? You mean you won't be making use of the permission Oyakata-sama has granted to you? I imagine he would be sorely disappointed to hear that."

You hurry to correct her misunderstanding. "Ah, no, of course I will. I plan to do so once I complete my mission. I thought it would be better to work at my own house, and it might be a little far to be bringing the notes back and forth, but I'm sure I can make do."

"Your home, outside of headquarters?"

Shinobu points out the flaw in your plan in a nonchalant tone. You bring your forehead in a loud smack. You've completely forgotten you aren't allowed to bring out the notes you've gained access to. The order you received clearly stated you had to be at the Butterfly Mansion in order to read them.

"Right, how careless… it completely slipped my mind."

"You are welcome to continue making use of my laboratory," Shinobu says. "Or did you think I would dispose of your notes during your absence? How cold."

"That's not what–" You see the smirk plastered on her face. "You make me a little mad sometimes, Shinobu-san."

She glides over and gently pats your cheek. "As repayment, I'll allow you to continue using the room you're staying in."

You give her your startled thanks and watch her leave the room after tidying up her desk. The dotted rim of her butterfly coat trails behind her before she shuts the door with a quiet thump. You stand in place for some time, marvelling at the sudden turn of events. Even daydreams have never been this odd.

"FU-KI-YA!"

You wince at your Kasugai Crow's impatient tone. "Yes, yes, I'm going."