Rui has just turned 30 and is still single. She decides to give up on men, buy an apartment and live with her cat! She visits a real estate agency with this idea in mind, but it turns out to be her friend, Hitoshi, whom she has not seen in nine years. In fact, they once made a promise over drinks that "if we're both still single by 30, we'll get married," and Rui can't help but think about it. She thought Hitoshi had forgotten about her, but...!