One Piece: Unreal Adventure - Chapter 84: Sometimes it was honestly good being a hero.

“Are you my knight?” The silver-haired youth looked at the blonde girl before him and asked, his cheeks flushed red. This was their first encounter when he was only ten years of age.

“Are you my bride?” He held her in his arms, embraced the girl who had accompanied him for ten years straight. He was sixteen years of age.

“Are you my king?” He knelt before the throne, smiling foolishly as he looked at the girl holding the sword victoriously. At this moment, he looked like the boy he was when they first met.

“I’m fine without having eyes for you. The entirety of Camelot is for your taking.” Smiling soft and gently, he gave his eyes to the girl who lost her eyes due to the curse of the red dragon. He doesn’t regret it, he thinks. He was twenty years of age.

“So… Arthur… Artoria Pendragon, are you willing… are you willing to spend the rest of your life with me?” His voice was soft and clear as he reached out to touch her hand.

This was their legend.

- Description from Novelupdates

Lin En transmigrated into a magical world that resembled medieval Europe but had the power of magic.Here, magic could affect and control basic particles, which was based on scientific theories that served as magic formulas!The wizards, who were actually scientists, were struggling to explore the truth of the world under the chase and blockade of the church. Lin En’s arrival sparked a renaissance of the alternate world…The white phosphorus fire, known as the Flame of Hell, the liquid nitrogen field of extreme cold, and the resonance frequency that kills without a trace… A few years later, the Holy See gathered all countries to the city, known as the legendary wizard, the pioneer of magic Lynn under the gaze of a group of wizards, wrote down the mass energy equation known as the ladder of God by later generations! Lynn looked around the crowd and said nonchalantly. “Mass and energy are interchangeable, and based on this theory, I have developed a powerful forbidden curse… It’s called — “The Big Nuke!”We will re-examine the world from the perspective of magic, where science is magic, and magic is science!

Hybern is defeated, but peace is not yet near. An ancient prophecy foretells the fusion of two souls. Nova, daughter of Feyre and Rhysand of the Night Court is to be joined with Hollis, son of Kallias and Viviane of the Winter Court. Without this union, it has been said death will claim the Fae lands, and in its destruction, all the Courts will fall.

Protagonist travels between different anime worlds to right wrongs and uncover his reason for being along the way.

- Description from Novelupdates