Everyone around Mia is getting married. She also wants to marry her boyfriend Shinpei, but he feels he's not up to the responsibility. At a wedding, he suggests a solution: a three-person marriage.
After Takuzo declines Mia and Shinpei's marriage proposal, he goes to a matchmaking party, but it goes horrible. Shinpei encourages Mia to talk to Takuzo again.
Mia and Shinpei move into Takuzos apartment. Now they have to figure out what this means for their intimate relationship, how to live with each other's quirks and how to resolve disagreements.
Now that they've settled into living together, new difficulties arise. Jealousy becomes an issue. Can a conversation between Shinpei and Takuzo improve the situation?
After the events of the previous night, Shinpei and Takuzo spend the day together and become a lot closer. Mia doesn't like them spending time together without her.
