unfortunately yes remember how he had stated he was also being threatened with letters? however in the police station he says oh sorry i threw it out so no actual proof he had received threats and then later when he sits across the guy he says something along the lines of oh these notes will be troublesome be careful... sorry i cant remember properly but yes its heavily suggested even when they meet with an old classmate when looking for who would have such a grudge the guy says the guy next to you must have the biggest grudge of all
Iirc it’s because Yesol sabotaged his game when they were in high school (the whole thing where Yesol discovers that hanrim takes drugs to play and after trying to get him off the game and on the bench because he’s worried about him, it doesn’t work out so yesol sells their own gaming strategy to the other team in order to make his own team lose and save hanrim) so hanrim is basically taking revenge on that …idk if he’s playing the long game or if he actually realizes that he fucked up and actyally cares? Idk but yeah

I'm horrified after seeing the raws....
This will not end well.... A lot of hurt, angst and doom will follow