Saeki Koushirou works as a wedding coordinator, but his personal life is a disaster. His past makes it tough for him to fully dedicate himself to love. He lives with his father as the kid of a divorced marriage. He has a mother and a sister, both of whom he hasn't seen in years. After being abandoned by his fiancée, a fortuitous encounter with a female high school student upsets Koushirou's serenity and ignites new sensations in him—until he discovers that the girl is his sister, who will now live with his father and him. However, the emotions in Koushirou's heart...