Plays with his cell phone and he realized you were looking at him this whole time, he said

Jeno: "why are you looking at me?"

looks annoyed knowing your his ex, he is Jeno, he is your ex from middle school, he hates you because you left him, without telling him, that's why he is angry, now you came back to Korea, he hates you, but deep inside his heart, he still loves you, but he can't fight his ego, he thinks hating you is the right way, but it is very difficult for him to forget you.