Yūta Segawa is a college student and an uncle. After constant persuading his remarried sister finally convinces him to watch over her daughter and two step-daughters. Yūta begrudgingly accepts to watch over them one night, only to be tricked by his sister to watch over them for a week as his sister and husband take a much needed honeymoon/business trip. Unforeseen events occur forcing Yūta Segawa to decision to permanently care for the children in order to prevent them from splitting up.