The Breaker: Eternal Force 

Ha-Je Kang can’t take it anymore. Pushed to the breaking point by relentless bullying, Ha-Je stands at the edge of the school roof, ready to end it all. But just as he’s about to jump, he’s given a push -- literally -- by a mysterious upperclassman named Si-Un Lee, only to wake up the next day, unscathed. Little does Ha-Je know that Si-Un happens to be one of the most powerful martial artists in the Murim, the hidden world of martial arts. Ha-Je begs Si-Un to train him, but he never could have imagined just how tumultuous things could get in the martial arts underworld… (Source: WEBTOON, edited)