After traversing to the apocalypse, I am extremely delighted as a Demon Cultivator - Chapter 48

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

The protagonist travels through Shu Mountain and becomes a demonic dragon guarding the heavenly book in Dinghu Peak.

A character with extreme difficulty and the worst performance, Baek Yu-Seol was considered tr*sh in the game because he couldn’t use magic in a fantasy world where everyone else could.

However…

[Due to the wrong ending, 90% of Aether World has been destroyed.] [Please reach the ‘True Ending.’]

Suddenly, those words echoed in my mind before I was transmigrated to the Aether World.

[You can use the skill ‘Flash’.]

“Why did I possess this character?”

Flash was the only magic skill I was given.

Surviving in Stella Academy where many genius mages ran rampant, I became the notorious Flash Mage.

11-year-old Jung Si-woo always had to play alone during PE class.

“I’m excluded from any ball games.”

“Are you kidding me? Why are you the only exception?”

“If I play with the rest, everyone will be excluded. Physically.”

The strength that Jung Si-woo has is not from any hard training but just a power he was born with.

When he turns 16 years old, the world faced a cataclysm, a huge castle appeared over the Earth out of nowhere. It began selecting special humans to grant them wings making them a Player and that soon changed the world.

10 years passed.

Jung Si-woo with a supernatural strength has still not been able to forsake his dream to be a Player. While he was enjoying his jobless life, he saved a falling Player and unknowingly met the requirement to be a ‘Underground Player’.

He became more special than anyone ever is! Now, Jung Si-woo brilliant dungeon strategy play begins.