When Jin was almost thirteen, he attended a classmate's birthday party and played Spin the Bottle.
When the bottle landed on Jin, he got his first kiss on the lips from the girl who spun the bottle.
This happened several times during the game, with different girls who would deliberately spin the bottle so it would always land on Jin.
Jin was a good-looking boy, the best-looking in his school, so girls were always trying to find ways to get his attention and kiss him.
That day, after several kisses in Spin the Bottle, Jin realised he didn't like kissing girls.
Kissing girls made him nauseous.