Yuu Arahama has five sex friends, one of whom happens to be a co-worker. One night, she asks him to marry her, but he rejects her, saying that he only sees her as a sex friend and also admits to his relationships with the other four women. Out of anger, she contacts them and ask them to meet and settle everything. But it happens that none of the other girls wants to break-up with him, because they also want to marry him, so they all ask him to chose one of them.
I guess the best old series with good end. 🙂