He eyeing Ideum and when the swimming teacher mentioned how Jaeyi asked to take care of Ideum, he was, idk, nasty? Like, he plotting something. Arggghh, I don’t want Jiseong to ruin something, Jaeyi is visibly can’t realize he is already in love, because he thinks it’s inpossible, and he also said, he doesn’t know how these feelings are like, but ahhh
I don’t think that’s a given, there’s a jump between them outside and them at the lockers, so he most likely introduced himself. He would’ve said something like “how do you know my name?” otherwise, and he also mentions how Ideum “said” he’s in the beginner class yet we didn’t see that part of their conversation as well

Everyone’s debating if the brother is the guy from high school nobody noticed that he already knew Ideum's name