have traveled to the eve of the night of genocide and am about to face the slaughter of the most filial sons in the ninja world. What should I do?

Official version of the introduction:

Traveling through time is a happy thing, and entering a familiar world is even more delightful. This double happiness should be a happy ending.

Unlike his predecessors who traveled here, Uchiha Shinki does not want to save the Uchiha, nor does he want to interfere in the struggle between the Uchiha and the Konoha high-level officials.

Uchiha Shinki only wants to live forever in this world.

But these two dogs, Sarutobi Hiruzen and Shimura Danzo, are really annoying!

Standing on the sterile table: "I'm sorry, Sandaime-sama, it seems that you can only be my experimental material."

In order to survive the night of genocide, Uchiha Nanhe, who had no cheat code, prepared to make his own cheat.

Through constant self-suggestion, when he finally awakened the Mangekyō Sharingan, the pupil of the soul responded to Uchiha Nanhe's expectations, and he obtained the Uchiha's ultimate pupil technique: Izanami, who turned reality into dreams, and Izanami, who turned dreams into reality...

In the world of ninjas, Sai Ueno became an ordinary cannon fodder Chunin, born into a common family, with mediocre chakra and only knowing the basic Transformation Technique.

Faced with the monopoly of ninjutsu, lacking both a ninja clan bloodline and a special ability, in order to survive better in the Second Ninja World War, he could only deconstruct the Transformation Technique using scientific thinking.

While the higher-ups of Konoha were busy harvesting cannon fodder with the Will of Fire, he derived the Beast Mimicry Breathing Technique from the Transformation Technique.

When the genius of the ninja clan was rampaging with their bloodline limits, he extracted the Human Puppet Bloodline Clone from the Shadow Clone Technique.

When the Six Paths' staff clashed with the Flying Thunder God Technique, he derived a quantum teleportation technique that was nearly akin to the Heavenly Hand Power from the Substitution Technique.

...

This book is also titled: "The Survival Counterattack of a Common Ninja," "Beast Mimic Transformation..."