Chapter 19: Regenerative Serum

I made the same evil smile that grandpa used when he was going to make my training harder. "You don't have to worry, so let's start."

"First since the core, it's the most important part of the body to fighters let's start with it" I clapped my hands and made the area around the training field have lower oxygen levels "You will have a hard time since I lowered the oxygen levels around the training field. First, you are going to do 500 sit-ups."

"Wait-What? Izuku-san doing that number of sit-ups with lower levels of oxygen it's crazy" said Kenichi

"It's alright you have the breathing technique, so you're going to be able to do this simple exercise," I said with a smile.

"Shut up karate kid, just do the damn exercise," Said Katsuki annoyed by Kenichi's complaint.

They started to do the sit-ups and around the 300's they started to have some troubles, I must say that now I somehow understand why grandpa was always smiling when he trained me.

"It took them around half an hour to finish and they looked very tired "Well done everyone, take 5 minutes to rest before we continue with the rest of the training".

Kenichi could only sigh in helplessness since he didn't want Katsuki to yell at him. The 5 minutes passed very quickly from their perspective but the training has to continue.

"Now that you rested, we are going to do push-up plank alternating should touch, like before you are going to do 500, but remember to wait 10 seconds between each arm change."

They started doing it and I could see that around the 200 rep they started to shake.

"Come on guys, you can do it using the power of youth! Also, remember to keep the breathing pattern"

"I hate when you fucking say that" Said Katsuki annoyed.

"Izuku-kun this maybe sound kind of dumb, but what is the point to do the breathing technique if the amount of oxygen around us is lower than usual, wouldn't be redundant to do this de-gozaru? Asked Kenshin

I sighed at Kenshin's question " You see even if you are doing the breathing technique, the amount of oxygen that enters your body is still low so your lungs work harder, also since you are still getting familiar with the breathing pattern this helps you to train it. Doing this triples the efficiency of the training, since you are working your core, lungs strength and practice the breathing pattern all in one exercise." I said with a proud smile.

After a few more minutes they ended the exercise and they look more tired than before, well it's obvious since I didn't give them too much time to rest. "You're doing great guys, rest another 5 minutes so we can continue"

No one said anything since they wanted to focus on replenishing stamina. Maybe this training seems basic because it is, I know more complex exercises that can help them but I want them to do simple exercises to get used to the breathing pattern while moving different parts of their body.

After that, they did a few more core exercises and I decided to end this part of the training. They are lying on the ground from exhaustion. To be honest, they are doing better than I expected, even if they are doing the basic, the low level of oxygen makes it harder for them to keep it, and training the core is tired itself since it works multiple muscles.

"Well you did it pretty well, to be honest, I thought that you will puke at least one time," I said with a kind smile.

"Don't underestimate us Izuku-kun even if it hard we will follow the whole training-de gozaru" Said Kenshin

"That's right it may be hard, but I will do whatever is necessary to become stronger." Said, Kenichi

And to my surprise, Katsuki was very quiet. I think that he knows what is coming next.

I made a big smile at everyone "I'm glad that you are full of determination, since that the case let's start with the next part of the training"

At this time the brother's faces become stone and Katsuki only sighed at my words.

"I-It wasn't over, hey Izuku-san tell me that you are joking," Said Kenichi with a pleading face

"Izuku-kun this is not a funny joke – de gozaru," Said Kenshin with a face of disbelief

"How can I be joking with training-related things, the whole reason that I taught you the breathing technique first is so you can keep with the training, and don't worry about anything the training is designed so you can keep it without getting any injury," I said with the same smile that grandpa used to do.

"Demon"

"Demon"

"Demon"

The 3 of them said exactly the same one after another.

"Just for this, I would increase the amount of training you are doing," I said joking

"NOOOOOOOOOOOO!!!!" Kenichi screamed at the top of his lungs.

After my 'joke' they continue their training for 2 more hours and they completed everything without failure. I'm glad that I made the right estimates so they won't have an injury, even if I can heal them with Kaidō, I don't want to hurt them without a reason.

After the training was over we went to the dining area, I prepared their food in a well-planned diet to supplement their training. They can have some snacks but only once or twice a day.

"Here is your food everyone, I planned this based on the nutrients that you will need to keep the training, this meal was created based on my mom's food, so it will taste very good"

Without waiting anymore, everyone started to eat the food ferociously. It's not a surprise considering the amount of training they did today.

"So good, as expected of your mom's food it's always delicious -de gozaru," Said Kenichi enjoying the food.

"No one cooks better than your mom Izuku-san," Said Kenichi with food in his mouth.

"Don't eat with your fucking mouth open, it's disgusting as hell!" Said Katsuki

After eating everyone wanted to go to their respective rooms but I recommended them to go to the springs near the training field since it has healing properties and will help them with their body heaviness, so they decided to go the brothers wanted me to join but I rejected since I needed to do other things.

I went towards the Shinigami Research and Development Institute building to start my experiments. In this place, I stored all the materials that I gather this couple of weeks, but I will not use them for the moments since I want to practice first with Reishi materials.

My top priority in recreating Hojiku-Zai that is the regenerative serum, even if a can heal almost everything with Kaidō I can't regrow limbs with it. So, I want to recreate this as soon as possible in case something bad happens. Maybe I can heal All Might with this in the future I can improve the condition of his lungs with Kaidō but to fully heal him I need to restore his stomach, but I will wait a little bit more since I still want to know a little more about him as a person.

If this gets known to the outside world, everyone will try to get it whether are Heroes, Villains, doctors, corporations, etc. So, I can only use it for people that I care about or trust and maybe as a bargaining chip when I need to negotiate with someone.

I get the basics of how the serum works; it promotes the creation of highly proliferative stem cells with the ability to regenerate any part of the body. But the side effect is that hurts a lot, so a person with low pain tolerance would faint but considering that it would regrow a limb, it's a small price to pay.

I have all the instructions to make it so it won't take a lot of time to do it, the only tedious part would recreate all the elements necessary to do it with materials from my world but luckily, I just need time to do it since I have all the equipment necessary for that in this lab. If possible, I will try to eliminate the side effects, I can practice with human bodies made of Reishi but knowing if the pain would be eliminated would be a challenge.

I tried for a few hours to make the serum, but I was unsuccessful this time, even with the list of materials it's a very delicate process that one mistake would ruin everything. I wasn't discouraged by this since I knew for the first moment that this was going to be a challenge. Some parts of the process took a long time so in the meantime, I started the first steps to create the Data-gathering Bacteria since it would be really helpful when I need to recollect information of the enemy base. I could let them go and recollect information about its hidden place and the people he works with.

I stayed in the lab a few more hours but since it was quite late I decided to go to my room to get some sleep, currently, it's 3 am and the training would start at 8 am, so I still have 4 hours to sleep that is more than enough after my body changed I only need about 3 hours of sleep if I don't do something physically strenuous.

The next day everyone woke up at 7 am to get ready for training and after having breakfast we went towards the training field. Today's training will be something interesting but before we could start.

"Excuse me Izuku-kun, I have a request – de gozaru. Said Kenshin with a serious tone.

"How can I help you Kenshin, if you want to increase the amount of weight, I can't do that for the moment," I said thinking that he ask to increase the difficulty of the training.

"It's not that Izuku-kun, I want to ask if you can show us your powers, you told us a little bit about them, but I will really appreciate I could see them with my own eyes - de gozaru." Said Kenshin with a firm resolve

"Okay no problem," I said instantly

"Don't you think that you responded too quickly?" Said, Kenichi

"Na, it's okay I was planning to do it anyway since we are a team, and we need to know what we are capable of," I said with a calm voice.

"Well, I told you about Shinsō and Hyōrinmaru, so I would show you another of my Shikai." I summoned my spear and pointed it towards the sky.

Everyone was paying a lot of attention to what is about to happen since they were curious.

"Make the heavens tremble…. Raikou!"