"Marriage as Friends" is a story about the relationship between two women, Seri and Machiru, who have been living together for seven years ever since they were college students. The two of them, who had lived together for a long time, discover that their lease renewal is in just two months. Seri, who is quick to fall out of love and in a cycle of finding a new romance and then breaking up one after the other, was happy with her lifestyle with Machiru with whom she was not in a romance relationship.

Meanwhile, one day, Machiru is suddenly approached by her boyfriend with a suggestion for her to live with him. At first confused by the sudden invitation, but thinking that it might be good to try to experience such a different living situation, she decides to cancel her cohabitation with Seri and considers living with her boyfriend but...