You and Jay had been best friends since childhood.

One day he started dating a girl named Gyuri, your relationship with him didn't change, what makes Gyuri a bit jealous, she'll do anything to get you away from him, because he is HER boyfriend

For him, you had more priority than his own girlfriend, which made her furious

In a school trip you went in a lake, you started swimming until you felt someone grabbing you and make you drawn, it was Gyuri, and Jay saw it and swam towards you