When Segawa Yuta entered university, he already had experience living alone since his sister Yuri married a middle-aged man during his junior high years. Yuta's parents had died earlier, leaving him solely in his sister's care. Unexpectedly, Yuri visited Yuta and entrusted him with the care of her three daughters while she went on a trip with her husband. Despite his initial hesitation, Yuta agreed. Unfortunately, while Yuri was away, her plane went missing. Yuta did not want to separate the girls from each other so he decided to take them in as his own daughters. Now, the unusual family lives together in a small apartment and adjusts to their new life.