Not a friend - what do I call her as?

Sinopse

Christmas Eve at the age of 21. Geon-woo, who is a single this year as always, has no thoughts on the suggestion of his childhood friend, Haru, to spend Christmas Eve together. “Remember when we said we should help each other if we were single until we were 22 years old…?” A different girl-friend's erotic dress, and sexy underwear that looks seductively? Geon-woo's heart starts to race as if he's about to burst at the sight of Haru's temptation as if crossing the line!