When Tatsu began training, the first thing he decided to improve was chakra control. Therefore, he started with things like walking on water, holding leaves on his forehead, and walking on a straight wall. While doing this, he also observed himself with Tenseigan and learned from his mistakes, quickly progressing. After being satisfied with his chakra control development, he moved on to other things.
"Alright, enough chakra control for now. I should be at least in the top 5 in terms of chakra control, as shown in the canon of the series I know. But now, what should I train?" Tatsu didn't know what to train next. After all, he wasn't an expert in training supernatural powers, and he had only been training for a month. But he came up with an idea.
"In the future, those damn Otsutsukis either suffer serious damage with senjutsu or taijutsu. I can't practice senjutsu right now, but taijutsu is a different matter. However, first, I should strengthen my physique." Upon this, Tatsu spent six months increasing his physical strength. But not only that; during these six months, he went to various battlefields and integrated the movements of others by copying them with Tenseigan. Yes, Tenseigan doesn't have the direct copying ability like Sharingan, but its insight allows him to copy taijutsu and A-rank and below ninjutsu.
"Alright, now I'm good enough in taijutsu, and I've also copied some nice techniques. But now I should work on nature transformations, and it's also time to develop Rasengan." As Tatsu pondered this, elsewhere, a completely black entity with only two yellow eyes was thinking about him.
**Pov: Black Zetsu**
"How, how could someone awaken the Rinnegan without my knowledge? This can't be happening." The entity known as Black Zetsu was pondering on the power Tatsu displayed. It was almost impossible for someone to awaken the Rinnegan unless he intervened personally. But now someone had succeeded, and according to the information he gathered, this person was not an Uchiha. Instead of their iconic black hair and obsidian eyes, he was a man with golden-yellow eyes and white hair. As he contemplated these events, Tatsu continued his training.
**3rd Person Perspective**
A year had passed since Tatsu started training. While eating the rabbit he seasoned and cooked, he spoke to the system.
"Hey system, what's my current level?"
[Ding! Due to low chakra levels, in combat, your current power level is that of a high Kage due to inexperience, although your rank is Super Kage.]
Tatsu was surprised to see this. It seemed he would become a Super Kage earlier than planned, which made him happy. Suddenly, he remembered gacha points and asked the system.
"System, how many gacha points do I have now?"
[Ding! Your server currently has 12 gacha points. Would you like to use them?]
The system asked, and Tatsu thought and replied.
"Just do a 10-pull for now. I'll use the remaining two points later."
[Ding! Understood. Starting a 10-pull. Reminder: With every 10-pull, one S+ item is guaranteed.]
As Tatsu grinned, ten wheels appeared in front of him and started spinning.
[Plasma Release] A
[500 Kunai] D++
[1,000,000,000 Ryo] C
[Swift Release] B+
[2000 Shuriken] D+++
[Shibuki] C+++
[Pure Otsutsuki Bloodline] S+
[Dust Release] A++
[Storm Release] B++
[Bashōsen] A
When Tatsu saw these, he froze, especially at the Pure Otsutsuki Bloodline. After his surprise, an incredible power spread through his body, and he began to evolve. Two horns grew on his forehead, and his skin turned almost pure white. When the evolution stopped, Tatsu immediately asked the system for all his current values.
[Ding! Your chakra level has reached the level of the lower six paths due to the magnificent increase in your physique, and your taijutsu has reached an incredible level, reaching the level of the lower six paths in comprehensive power. Your current lifespan is 10,000 years, and if you find a suitable vessel, you can be reborn by implanting a Kama into it. With this reward, you have also gained: Kama, Super Regeneration, All Nature Transformations, Longevity, Removal of Human Limitations, and a Massive Chakra Reserve.]
When Tatsu saw this, he thought, "Training is no longer necessary. With just what I have, I'll probably surpass Kaguya in the Fourth Shinobi War as an adult, becoming Juubi's jinchūriki. But my appearance bothers me." Upon this, Tatsu asked the system.
"System, can you make my appearance the same as before?"
[Yes, the server wants this?]
"Yes, I want it."
Immediately after this, while maintaining all his power, he returned to his old form. But at that moment, he noticed that his eyes had become even stronger.
"System, why have my eyes become stronger?"
[This is because the server is now a Pure Otsutsuki.]
Tatsu nodded in understanding and spent three more months in the mountains to adapt to his current power.