They are neighbours, being friends since in diapers.

They were good friends. They were. But as soon as they enter high school, she began to distant herself. He noticed it but he didn't know the real reason. He think, that he should fix everything.

No. He really should fix everything. He can't afford to lose her. Not when another feeling grew inside him. 

I, Oh Sehun, vow to fix our bent-but-not-broken friendship. And maybe, doing some upgrading.