Captured Hearts: The Substitute Bride's Gambit - Chapter 275 - Wen Nianyou Reveals Her Identity

Nagasawa crossed to Naruto Universe and was bound to Konohagakure.If Konoha is severely damaged and destroyed, Nagasawa’s lifespan will be reduced.He panicked at the thought of the upcoming Nine-Tailed Demon Fox's attack , and the thought of Konoha getting destroyed left him in despair.Fortunately, while bound to Konoha, he can obtain templates of powerful characters.At the beginning, He got the Whitebeard template! Since it's the Whitebeard from the Summit War of Marineford, he can use Tremor-Tremor Fruit's ability and Haki.Facing the Tailed Beast Ball, which terrorized Konoha Shinobi, Nagasawa leaped and shattered the Tailed Beast Ball with one punch!

Humanity was on the brink of destruction. Muyoung, an assassin from the Forest of Death, fell to his knees. There were corpses all around him. For years, he had worked for the Forest of Death and had finally been able to eradicate them. Now, he, himself, was about to die. He closed his eyes as he felt his heart stop beating.

Some say reincarnation is a blessing, but for me, it's a dreadful curse. Cursed with endless reincarnation, I've been reborn as a villain 137 times. And all 137 times, I've been toyed with and killed by heroes who are far more cruel than the said villains... If I can't win no matter what I do, then I'll crush those so-called heroes at their very roots. - Quality Fan Translations, Made by Fans for the Fans - Villain Takes Over The Academy

He rose from abjection and achieved eternity in glory.
He embraced the prettiest beauties and killed the strongest opponents.
He was able to shift the clouds into rain and cover the sky with one hand.
He could overrun the entire world and go anywhere as he pleased.
He pacified wars and held the world in awe.
He was matchless in the world.
However, his hair turned white overnight for his beloved woman and he was on the verge of death.
He was surrounded by enemies who were trying to take his life.
He struggled his way to become mighty and fought for everything he cherished.
For this age, he was the only king of the Dark World.
His name was a byword for might.
As a man living in the world, his only ideal was to pursue brilliance.

- Description from Novelupdates