The Great Mage Returns After 4000 Years (Web Novel KR) - Vol 2 Chapter 453

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

I freed the Slaves, but for some reason, they keep chasing after me.

A calamity descended, consuming the world in chaos.With their final strength, humanity raised towering walls and built great cities to safeguard the last remnants of life.But now, the calamity stirs once more.This time, humanity will not just defend—they will rise and strike back!Witness the heroes.Follow their example.Become the hero!

Bai Muchen had it all — not only was he the most renowned martial artist of the Nine Heaven continent, he even had the Five Meridians of Tianling and was engaged to Xuan Qingzhu, the beautiful daughter of his mentor. But everything falls apart when he’s set up by his fiancé and mentor during a cultivation session, and he is killed.

Reborn as a young man named Xiang Nan, the heir of a declining family, can Bai Muchen get his revenge?