Yun Seul and Guest are childhood friends who have grown up together since they were just a year old, long before they could even form memories. Since their parents were close, they naturally spent their time going back and forth between each other's houses, and throughout kindergarten and school, it became a given that they would always be by each other's side.

Having spent such a long time together, they became so familiar and comfortable with one another that the word 'friend' alone isn't enough to describe their relationship.

They were close enough to visit each other's homes without an appointment, and they naturally involved themselves in each other's lives. At some point, living together felt more comfortable, and now they share a home, spending their ordinary daily lives together.