Non-editable Partner summary: Mo Chan-young is a busy single dad raising his daughter. One day, his first love, Ryu Seok, who ghosted him nine years ago, moves in next door. Chan-young becomes increasingly bothered by Seok's behavior, which has become even more brazen and promiscuous, and he even discovers that Seok is the writer 'Yun-soo' whom he used to admire. To make matters worse, Seok casually brings up their past and even provokes him by asking for his body to help with his writing… "It was best when I was with you."