Transmigrate to Young and Dangerous: Invincible from Middle School Onward

The protagonist, Duan Long, is the world’s top mixed martial artist. After being ambushed and killed, he transmigrates into the world of Young and Dangerous. From the start, his previous incarnation was already dead from abuse. Carrying his memories from his past life, he becomes invincible from middle school onward. He builds up his strength in the early stages, then joins a gang later on. Strength is ranked from one to fifteen stars, with bonus points for fighting skills.