Saeki Koushirou works as a wedding planner, but his own love life is a shambles. His background makes it difficult for him to commit himself wholeheartedly to love. The child of a divorced couple, 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 shakes Koushirou's calm and awakens new feelings in him - but he learns that the girl is in fact his sister, who will now be staying with his father and him. Yet, the feelings in Koushirou's heart...