He wasn't really willing to open up his character to anyone.

He hid his name, played his part being Seronick,who died months ago, he was his doppleganger. He wanted to stay in the background and watch the play. He acted studious, quite, or what you call nerdish and everything like Seronick. He was doing his best until he met her. Kim Sarang, the girl who was quite famous for freaking people out.

Sarang Kim- girl who loved solving the mysteries. She thought whatever Seronick(the new one i.e., Sehun)did was all fake, she thought he was hiding something,she tried convincing it to many people,but they either didn't care or they ignored. She was growing very curious about him day by day and on the way,she didn't realise that she was in love with him.