MTL - Harue Kagetsu - Chapter 46

Quinn Winter is a young man from another world. One day, he is suddenly chosen to become the new Demon King. But the Demon Kingdom is in big trouble – it's losing a terrible war against the human kingdom called Gran'le.To help his people, Quinn comes up with a risky plan. He will sneak into Gran'le and learn their secrets. But things don’t go as planned. A powerful noble sponsors him, and he ends up joining Heavenward Academy, the top school for training future heroes.At the Academy, there's a big challenge called the Selection. The best students become Paladins – magic knights who fight demons. Quinn doesn’t want to become a Paladin. He is a demon king! But now, he’s stuck in the Selection… and if he wins, he’ll become the very thing he’s supposed to destroy.He started the day badly. Now, things are getting even worse.

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.

Lou Yao Yao wasted her life fighting over a man, only to find out he wasn’t worth it in the end. Because of this man, she accidentally killed her rival in love, and even ruined the man who had always been watching over her.

Getting reborn as her 20 year old self, there is still time to fix everything. Lou Yao Yao decided to live as a genuine vicious woman. After getting her hands on the loyal like-a-dog man, she would show that cheating couple what pure loving affection looked like.

- Description from Novelupdates

The MC entered the body of the An family eldest son, An Ziran, an arrogant 16 years old boy who weighed 78 kg (~171-172 lbs), who only knew how to eat, play and sleep. Seeing his current body, An Ziran decided his first priority was to LOSE WEIGHT!