Belle Adams' Butler - Chapter 398 - Track Of Time- Part 1

I finally managed to kill the demon lord.

In a peaceful, utopian Earth, a young man is born cursed by the will of the heavens. One day, he awakens… and uncovers the hidden world of the High Humans—the most powerful beings on the planet. His superpower? A rare support ability with healing powers… or is it? From that moment on, a healer who devours lives to grow stronger, just like the worst demons, is born. *** This is a story about superpowers in a distant future, where Earth hides unimaginable secrets. It’s also a journey across universes, filled with battles and discoveries. The protagonist isn’t a genius or a trained warrior. He’s just an ordinary man who faced dark times and watched his life be consumed by the abyss. But now, he has a chance to change everything. Step by step, he will learn why to fight—and how to survive.

Xia Yan passed through to the world of Bleach and became an eleven-year-old boy. He was rescued by Renji and Rukia in the Seireitei, and he was studying at Shin’ō Academy, and he was a student of the same class.
He is a top student of the Shin’ō Academy, and he is vying for strength by various teams. In the end, he has entered the first team of secret mobile maneuvers.
He will use punishment to kill every person who tries to threaten the martyrdom and protect his loved one.

- Description from Novelupdates