Toaru Majutsu no Index - Volume 7, Epilogue: End Action. The_Page_is_Shut.

Two years ago, Xu Xuan was the No.1 genius of the Xu Family and was rather famous among the young generation in Cloud City. His mother died of illness when he was a baby and he wanted to be father’s pride. That was why he challenged the person with the much higher cultivation in the martial arts competition.

Unfortunately, Xu Xuan lost. And his dantian was broken by vicious enemy. But he didn‘t reconciled at all. For the past two years, he had but he had persisted in cultivating every morning in the hope that there would be a miracle. However, there is not until he met the superior of Mysterious God Realm who was escaping. After a fierce struggle, Xu Xuan swallowed unique treasure Nine-Swallowing Divine Jade and obtained a low-grade Heaven rank cultivation technique Five Spiritual Arts.

Xu Xuan would never forget the scenes of how the marriage was annulled yesterday, nor the disdainful gazes of others, let alone their smiles after his dantian had been broken. What legendary road will this ordinary boy from the wilderness embark on？

- Description from Novelupdates

Li Xuan traveled through the world of immortality and opened the apprentice system, and both apprentices and apprentices could be rewarded for upgrading.

【Ding! Accepting apprentice Qin Yue, reward you: Innate Divine Power]

【Ding! Accept the apprentice Zhao Tian, ​​reward you: call the wind and call the rain]

【Ding! Apprentice upgrade, reward you: space shuttle]

….

Li Xuan, who accepted a bunch of apprentices, evolved infinitely in seclusion.

Ten years later, the Devil Emperor invaded and wanted to sacrifice the whole world, but no one could stop it. The disciples watched the world fall into despair in pain.

At this time, Li Xuan appeared and slashed a sword against the Demon Emperor under the watchful eyes of the public.

Boom!

The sky fell apart, the invincible Demon Emperor fell on the spot, and the entire dark world was swept away by a sword.

The disciples were horrified. It turned out that the strongest person in the world was actually the master who had been in seclusion for ten years.

- Description from novelbuddy

When a person dies, they either die light as a feather (aka unimportant) or heavy as Mt. Tai (aka very important).