JB and Junior are brothers that are very different from one another such as Jb likes to be alone and do his own thing while Junior likes to hangout in group. Jb doesn't like telling people things such as his personal life and no one knew he had a girlfriend, when they broke up he was hurt and decided to play Joy who was the cousin of his ex girlfriend Suzy. Joy not knowing that her cousin Suzy and Jb dated she accepted his confession as he went public with her, Junior who knew of this didn't like what his brother was doing but he doesn't listen to anyone and let it be. Six months into their relationship Jb slept with her and just moment after he told her the truth why he dated her was to get back at her cousin Suzy who Joy was really close too. Joy was devastated and ran out of their house in tears bumping into Junior on the way down.   

JB

Joy

Junior

Suzy

Seulgi

Wendy

Jackson

Mark

Yugyeom