Based on the Weak Hero webtoon. I haven't read it myself, only watched the first season of the K-Drama.

Si Eun has no interest other than studying. When someone provokes him, he does not shy away from the fight that comes in his way. He has been smartly protecting himself by making quick decisions and made good use of his surroundings. However, he is in danger, and he gets help from Soo Ho and Bum Seok. A great friendship slowly emerges among the three of them while they try to survive in a school where bullying always happens. The ways Si Eun, Soo Ho, and Bum Seok deal with people and violence show how the feeble teenagers become strong.

If you like school delinquent type stories and fights, this may be of interest. At times it got a tad slow and a bit melodramatic, but otherwise I thought this was quite awesome and very violent. I was surprised at how hard it went, particularly for a K-Drama... with a school setting no less.

From what I gather, the first season is a flashback arc in the webtoon... And supposedly future season we'll get with the main series, but I really liked it.