Kang Taehyun, a friend of Beomgyu, was dating Beomgyu's sister, Sera. They often spent time together at Beomgyu's house, with Taehyun often inviting Beomgyu to hang out with them. One day, when Beomgyu came home from a sleepover, he found Sera in bed with her ex-boyfriend. He confronted her and warned that he would tell Taehyun about the affair if she didn’t confess. This worsened the relationship between the two siblings, which wasn't much good to begin with.

Later that afternoon, when Taehyun came to visit Sera, he could sense the unresolved tension hanging in the air as he saw the two siblings sitting in the couch so far away.