Nanao Shuuji left his hometown, where his family runs a well-known chain of supermarkets, to become a part-time teacher at a cram school. One day, the son of his father's mistress, Takatou Kazuomi, appears before him. Shuuji once confronted Kazuomi's mother and also injured Kazuomi as a result. Kazuomi made use of Shuuji's weakness in order to keep getting financial aid from his father. He accomplished this by blackmailing Shuuji into helping him thanks to a certain photo..?!