If it were a normal baby, having Uchiha Yoichi occupy the body would certainly go against the principles of a doctor, and Tsunade would never agree.
But the mission of this developing infant from the very beginning was this, and now it doesn't even have consciousness, using mainly the cells and genes of Uchiha Yoichi.
It's best to inject the consciousness now, otherwise when the baby naturally develops consciousness, it's really hard to say if it counts as murder.
"Spiritual Clone Jutsu!"
After Uchiha Yoichi performed the sealing, he immediately released a spiritual body from himself, which is a soul clone and carries chakra, different from ordinary clones.
Tsunade, watching this ninjutsu from the side, felt somewhat emotional, but it was merely emotion, she just hadn't expected Uchiha Yoichi to actually improve an S-Class soul kinjutsu.
Once the spirit body carrying chakra entered the infant's body, Tsunade directly used the Sealing Technique to seal the spirit body.
After completing all this, Tsunade clapped her hands and said, "Alright, in about three months it will be just like a newborn baby, and in a year it will be about the size of a seven or eight-year-old."
Uchiha Yoichi touched his chin and said, "It sounds like it grows pretty fast..."
"That's only natural; a normal womb doesn't have such abundant nutrients. Although you can inject additional nutrition to make the young grow quickly, while the body can develop, the brain can't develop along with it... but for you entirely, it's not an issue."
Tsunade explained that this cloned avatar has a mature consciousness, just limited by the body, so it can use a special nutrient solution to let the body grow quickly.
A normal baby would need a day of three meals plus excretion and sleep to grow to a seven or eight-year-old child, but this cloned avatar is different; soaking it in nutrient solution for a year is enough.
One year's growth is equivalent to ten times the growth rate of an ordinary person, and seven or eight years old is Tsunade's conservative estimate, with the need to adjust in case of mid-process issues.
'In about two years, I can transplant the Kamui Sharingan into the cloned avatar. But one eye isn't ideal, I should find time to take care of Uchiha Obito...'
Uchiha Yoichi thought to himself. The potential of this body is undoubtedly there, with Senju, Uchiha, Hyuga, and Dead Bone Pulse, it's almost an Otsutsuki Kaguya template.
Two years later, I'll start training Genetic Primordial Energy, which can make the clone even stronger.
"Tsunade, I'll be counting on you next. By the way, do you want a cloned avatar? I can teach you the Spiritual Clone Jutsu too..."
"I don't want it."
Tsunade slightly frowned and shook her head, saying, two bodies always felt weird to her, especially since one was a fusion with various Bloodline genes.
Were it not for Uchiha Yoichi's obsession with her body, she'd start to suspect if the shy little ghost was influenced by Orochimaru and didn't want to be human anymore.
"As for the Desperate Virus, trying it out according to the raw data you provided resulted in some products. However, the probability of self-explosion is just too high. Even if limbs can regenerate, the brain's programming system gets chaotic after excessive repair, then the test subject self-destructs..."
Tsunade rubbed her temples. While the effect of the Desperate Virus is strong, its side effects are terrifying. Even a single mouse self-destructing has about half the power of an explosive tag.
If it switches to a human, the destructive power would likely be stronger.
"Can it integrate with other Bloodline genes?"
Uchiha Yoichi suddenly remembered that when the Desperate Virus was initially researched, it was indeed imperfect. It only started mass production after integrating with another superpower user's gene.
"Integrate with other people's Bloodline genes?"
Tsunade frowned slightly upon hearing this and then bit her finger thoughtfully said, "You're suggesting using another gene to suppress the chaotic re-editing caused by the Desperate Virus repairing injuries excessively? But which Bloodline gene works best?"
"....Kimimaro's Dead Bone Pulse, or Shiro's Ice Release Bloodline."
Tsunade glanced at Uchiha Yoichi, then snorted coldly, "You want to suggest using my grandfather's Wood Release Bloodline, don't you? You and Orochimaru are both bastards..."
"It was Danzo's doing, I swear. He found Orochimaru and then Orochimaru came to me."
Uchiha Yoichi explained, then reaching out to embrace Tsunade, buried his face in her bosom, and murmured, "Besides, I'm not thinking like that right now."
Although the first thought was Hashirama Cells, he wouldn't admit it now; after all, saying to use her grandfather's body cells in front of his granddaughter doesn't quite sit well.
"Danzo is a bastard, and you're not much better~"
By the end, Tsunade's tone began to suppress her words, biting her lips.
Ultimately, she didn't rush to make up for it here, because Uchiha Yoichi's words had given Tsunade quite a reminder, that using another gene might indeed work.
Tsunade also hopes for the successful research of the Desperate Virus, so she can prepare a part for Nawaki too; if the shortcomings of the Desperate Virus are improved, it truly is a powerful genetic potion.
It can enhance the body two to three times and has recovery power comparable to her Strength of a Hundred Seal; if Nawaki injects the improved Desperate Virus, his survival rate can increase several times.
Upon leaving Konoha Hospital, Tsunade reminded Uchiha Yoichi to pay attention to Kushina.
It's a troublesome matter for a Jinchuriki to be invaded by the negative emotions of Tailed Beast Chakra, especially since Kushina is a sealing expert herself; even having the Sealing Key from her won't be of use, she can 'make a key' herself.