Microbugs

Kira was a programmer back on earth, not someone who knew a lot about cells and how organisms worked. Due to this, he decided to work under Orochimaru so that he could learn about all of this from him before he could start working independently. 

The first month, he silently listened to snake man's orders and did all of his chores while keeping an eye on everything Orochimaru did. He also took theory lessons from him everyday for a minimum of 4 hours.

His schedule was simple. Workout for an hour, theory lessons for 4 to 6 hours, working as snake man's assistant for a minimum of 8 hours and the rest was free time, which was barely any free time as he had to sleep for 8 hours as his body was still developing. 

The kids his age, moved up a year in the academy while Kira smiled as he looked at his system screen after he had invested the character point he got from reaching the age of eight.

His physique went up from C to B and he invested his extra character point he got from turning 8, into chakra control. He didn't need any more improvement in chakra control to use the flying raijin, but he still invested his points into it as he had other plans for it's use. 

'Once I get this to SSS grade, I'll be able to learn one of the most hardest jutsu's in the world. One that could rival the eight gates, but also has a lot of versatility.' he thought as he stared at his system screen, thinking about how he could achieve his goals.

[Character Talents]

Chakra control: S -> SS

Ninjutsu Talent: A

Taijutsu Talent: C

Genjutsu Talent: E

Physique Quality: C -> B

Physical Recovery: F

Chakra Recovery: F

Chakra Quantity: F

[Elemental Mastery]

Fire, Water, Wind, Lightning, Earth, Yin, Yang

[Unique Enhancements]

Dynamic Vision: None -> SSS 

Hashirama Cells -> SSS

The science of creating, cloning and manipulating cells wasn't easy. It was the same with modifying the kikaichu that he had. Thousands of kikaichu died everyday, but Kira boosted their reproduction rate by letting them consume his chakra.

At first, Orochimaru only taught him about the basics and didn't involve Kira in his projects, but as months passed and he saw how fast the kid was learning, he began to treat him like a proper assistant instead of a janitor. 

This wasn't normal ninjutsu or taijutsu which he could learn by simply practising or training for a few weeks or months. The subject was complicated, deep and unpredictable. 

As he worked with Orochimaru, he helped the snake man create an actual limb. At first, it made him want to strangle Orochimaru to death as these cells originally belonged to someone whom he completed life and death missions with. 

But for the sake of his future, he kept his emotions under control and as time passed, the curiosity and anticipation greatly suppressed his feelings of vengeance, but it wasn't completely forgotten. 

At first, he was angry at Orochimaru and wanted to kill him, but it didn't take him long to figure out that the man in front of him was just a person scared of death. At least, that was the simplest way to put it. 

He was simply in a pursuit to keep himself alive and why was this the case? It was because, just like Tsunade, Orochimaru also experienced terrible things in the second great ninja war. It was an unmistakable case of ptsd. 

When he realised this, his target changed from both Danzo and Orochimaru, to Danzo only. His plans changed too, as he made up imaginary scenarios where he'd inflict immeasurable amount of pain to the man who was the main reason behind his friend's death.

One by one, months passed by and there were minor breakthroughs in the two of their research. Especially on Kira's end as he was done learning from Orochimaru after 16 months and began his own experiments and research without snakeman's help. 

It took him another year to get the results he wanted and once he was done, he left the Root for good. As for Danzo, he had uses for him in the future. 

With long, unkempt hair and an extremely pale face, Kira walked out of the Root headquarters for the first time in more than 30 months. To be accurate, it was close to being three years since he had been holed up in his place. 

The first thing he did was to go to Hiruzen's office and as for the thing he gained from the past three years of dedicated research and hardwork? It was the nanobugs he had created using the concepts and specialities of half of the aburame clan's bugs.

It had the smelling capabilities of the Bikochu. Although it wasn't as good as the Bikochu, his bug's sense of smell was as good as a trained ninja dog.

It also had the abilities of both the poison bugs, Kochu and Rinkaichu, but they were a little altered. Like the Kochu, his bugs could secrete poison into a person's body and once the person dies, the poison disappears, making it one of the best poisons to ever exist. 

But unlike the the Kochu that could both paralyse and kill, this one did none. Instead, this poison was technically not a poison.

As for which part of Rinkaichu's abilities it got? It was to consume flesh and organic matter to multiply in numbers. The Rinkaichu's poison ability was lost during the process, but Kira was happy with the result.

Unfortunately, he couldn't put his flying raijin seal marks on them as they were way too tiny, but he managed to figure out another way to integrate flying raijin to his fighting style using his bugs. 

And that was done with the Kochu and Rinkaichu powers that his bugs had. By combining the Kochu's undetectable poison powers and Rinkaichu's poison spreading powers, Kira managed to biologically program this "poison" to act as a seal mark inside a person's body. 

[A/N: Yes, it's all BS and I know nothing about bioscience. But hey, this is fiction so just enjoy watching him become overpowered. Actually, now that I think about it, I feel like I made him too OP.... hmm...]

[A/N 2: Yeah, I'm nerfing it tmro, but he'll gradually get these powers. The only change is that he won't be getting all of them at the same time.]

[A/N 3: Due to multiple requests, I've decided to not take away key the abilities of these bugs. Instead, Chakra absorption and self destruction will be taken away. These might just come back in the future, or maybe these bugs will become even more stronger. Who knows?]