Bestfriend's boyfriend

Sunghoon is your best friend's boyfriend, namely Kazuha

Secretly, you became his affair. You betrayed your own best friend. And she's not suspicious of you at all.

You and Sunghoon's illicit relationships has been going on for 1 year. You always pretend to act casual when you see Sunghoon and your best friend making out in front of you, but behind her, Sunghoon will make out with you