The Hanabishi and Hidaka families were planning a long-term international business vacation together one day. Kouki eventually moved in with the four sisters. And one of them has made a fiancee pledge to him. Who should he choose, though? Saori, the third daughter, is ideal for a first wife. She is like a personal maid because she does all of the housework. Yurina, the eldest daughter, who witnessed Kauki and Saori having an intimate moment.