It's definitely Unnie's boyfriend remember he saw her looking at a guy that looked similar to him when they were out eating. I have a feeling he caused big brother to be in the emergency room.
Idk about anyone else but I low key relate with Yukiya a lot its really hard joining new friend groups if your slightly introverted, I like how he's finally trying to leave his bubble though.
Nah atleast he knows that she's jealous i've seen some dumbass mcs way worse than this that can't even tell when the girl is jealous or what she's feeling