Hearing that in return for getting the knowledge of removing Muzan's curse from the demons she'll have to reveal the knowledge of transforming humans into demons to this person she met literally an hour ago made her waver.

"That..." Tamayo hesitated, her voice carrying a note of uncertainty, "That is not possible, I cannot trust you with that knowledge."

Who knows what he might become with that knowledge in his possession? Another Muzan Kibutsuji? Something worse? Tamayo pondered.

Arthur let out a sigh.

If he could just turn Tamayo into an Infected Demon he wouldn't have to give so much explanation, but he couldn't, since she was someone he had to 'save'.

And he didn't know if turning her into an Infected Demon would result in a failure of the mission or not.

His gut says it will.

"If the safety of humans is your concern, then there is no need to worry. The beings I require for transformation, once I acquire that method, are not humans. They are my special summons. I can summon them at will."

Arthur took out an undead from his inventory, it looked like a decaying teenager. The dead donned a fancy yellow jacket, black trousers, and white sneakers.

Arthur waited for a moment for Tamayo and Yushiro to take in this detail and then continued, "They're absolutely loyal to me but they're too weak and can't do a thing unless I tell exactly what I need from them. I want to transform them into demons and see if there is any change in their aspects, that's all."

Tamayo fixated her gaze upon the undead creature, silently observing for a few moments before speaking, "Are these not just a manifestation of blood demon art, their cell structure should be the same as you?"

Arthur shook his head, dismissing her assumption. "No, their cell and DNA structures are entirely different, nothing like mine or any other demon's. That's why I think this ability of mine is something special, something unique. Like the ability of that Nakime, the Upper Four, her powers can tap into other dimensions."

Arthur couldn't exactly tell her that the undeads are from another world, that's why he had to make up a believable lie in such a way that it wouldn't restrict their research ideas and directions in the future.

"I think my power is something unique too. What I summon are humanoids but are neither demons nor humans. I call them undead by the way. As their bodies are rotten like dead corpses but can still move. They're really brittle too. But I see the potential of evolution in them, potential to rival Muzan..."

"Hmm, I see. 'That Man'  must've branded you a traitor since you broke his curse but now that you have managed to break another demon's curse, he must've deemed you a threat." Tamayo said looking at Ryoma who was having a staring/glaring contest with Yushiro.

Arthur also followed Tamayo's eyes seeing the two greenheads glaring at each other for some reason, not minding the two he replied, "You're right, he even sent Upper Three to execute me. That time I mostly got toyed with, just a playmate for that battle freak... until I managed to administer the 'curse-breaking solution' inside his body."

Tamayo nodded.

For the next few moments, she weighed her options and thought of the various possibilities but eventually chose to accept Arthur's proposal.

"Heito-San, I accept your proposal."

The deal was set and done, there was no need for any formal written contract-like thing to set the deal, just a handshake was all it took.

Though the veins in Yushiro's head nearly popped due to jealousy seeing his madam's soft hands grabbed by someone else.

The only thing that Arthur was gonna regret in the future is not having more undeads stored in his inventory. He had less than 20,000 in his inventory after all.

Anyway, in a few more days, just like Arthur, Shizuka and Saeko also completed the first step of their missions.

Shizuka's mission was to get into the Butterfly mansion along with Rika while Saeko's task was to convince Urokodaki into teaching her the Water Breathing techniques.

And while Shizuka and Rika got in pretty easily that was not the same with Saeko. Urokodaki flat-out rejected Saeko when she asked him to teach her, even that sad backstory didn't get through to him. On the first day, that is.

After Saeko persisted for a few more days, Urokodaki assigned a test to Saeko, a really really difficult test, which Saeko was barely able to pass.

In truth, Urokodaki didn't want to train students anymore as they would just serve to increase the number of casualties in the final selection exam, he accepted Tanjiro only because of Giyuu's request.

That's why he assigned such a difficult test to Saeko. However, upon her success, he had no choice but to accept her as a student and train her alongside Tanjiro.

The next few months passed calmly on all sides, Saeko trained and learned the Water breathing techniques, and Shizuka learned about the poisons and demon physiology.

And Rika, she was free to laze around all she wanted in the Butterfly Mansion, it was a really safe place, after all.

And the staff at the mansion let her be, as she was supposed to be the guard of the foreign blonde researcher lady (Shizuka). Though sometimes she had help in some odd jobs here and there.

The research at Arthur's side also went smoothly, with Tamayo's 200 years' worth of experience in demon genetics and Arthur's futuristic knowledge and equipment, the breakthroughs they made in a mere few months were bigger than any of the past.

Tamayo was greatly surprised by the types of equipment Arthur had, she was curious about their origin but didn't ask him where he got them from as she knew it'd be futile, he wouldn't tell her. Besides, she was just satisfied that the research was coming along nicely.

The main objective of their research was to create a serum that could transform the undeads into demons.

But Arthur was also working on something else simultaneously, which was kept secret from Tamayo — a way to overcome the weakness of the sun.

Arthur managed to get the blood samples of the whole Kamado family. Saeko gave him the samples of Tanjiro and Nezuko; while taking the blood samples of the rest of the family was quite easy as they were resting in his inventory.

But still, it turns out that finding a cure for sunlight was harder than finding a way to transform undeads into demons.

Nezuko's cell structure was constantly evolving so it was difficult to conduct research on while Tanjiro's cell once introduced with demon blood completely overpowered them.

It was like he was immune to demonic transformation.

But Arthur knew better, it must be something else! It had to be! Otherwise 'that scene' wouldn't happen in the final arc.

Still, this attribute that Tanjiro's blood displayed was key to creating a serum for turning a demon back into a human. Obviously, he didn't share his observations with Tamayo.

Aside from the research though, life was plain and simple.

During the day they would research demonic mutation, the undeads, etc. In the evening Tamayo and Yushiro would go to their clinic to cure some patients. Sometimes Arthur would join too.

His diagnoses were mostly correct and Tamayo would always listen to his inputs intently. He had helped in many difficult cases. Even Yushiro had to recognize Arthur's expertise in the medical and genetic department in par with his Lady Tamayo's.

Arthur would also make time to visit Shizuka and Saeko once or twice a month. They would exchange information, or just lie down in peace. Have some intimate times if possible.

And so a year passed... and the formula to turn undeads into demons was ready...

==================

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The new fic's out!  

Title: Marvel: I Need A New Body

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