This isn't a mindless power fantasy. It has multiple heroines, a complete system of ninja ranks and training, and a dual-world switching format. The pacing is a little slow, so proceed with caution if that's not your thing.
Uchiha Shiyuan is a transmigrator. Unlike other transmigrators, he has no System. He unexpectedly awakens the Sharingan, but while others use theirs to dominate the shinobi world, awakening his earns him a terminal illness.
His eyes won't close, his chakra is being drained at an alarming rate, and the once-proud Uchiha prodigy has become the clan's laughingstock, the "Shame of the Uchiha." He spends ten years bedridden, with death fast approaching.
To stay alive, he risks everything and uses the Reverse Summoning Technique without a contract!
He expects the summoned beast to tear him to pieces. Instead, when he opens his eyes again, he's in a strange otherworld.
Back in the shinobi world, not only is Danzo coveting his eyes, but the Second Shinobi World War is about to begin, and a genin of his strength would be nothing but cannon fodder. In the otherworld, gold leaves cover the mountains, and the life of a rich man is wonderfully simple.
Just as he prepares to keep his head down in the shinobi world and throw his weight around in the otherworld, he discovers that things aren't going quite as he expected.
Years later, Madara Uchiha watches his Perfect Susanoo get shattered with ease and begins to question his life as a ninja.
Madara: Is that really one of my Uchiha?
Black Zetsu: I think... so...
Shiyuan: Heh heh heh. Madara, I hereby declare you the strongest.
