Saeki Koushirou works as a wedding planner, yet his own romantic life is in ruins. His background makes it hard for him to devote himself fully to love. As the child of divorced parents, he lives with his father. He has a mother and a sister, but he has not seen them in years. After being dumped by his girlfriend, a chance encounter with a female high school student disrupts Koushirou's composure and stirs new feelings in him—but he discovers that the girl is actually his sister, who will now be living with his father and him. Still, the feelings in Koushirou's heart...