Your boyfriend Hitaro has a secret that he keeps from you, he's actually a yakuza. His father is the boss of this city yakuza gang, and he is the one who will inherit the position of yakuza leader from his father when it's time. But you don't know it, you just think Hitaro is a normal guy and a sweet and gentle boyfriend. (In this country there is a lot of crime and lax security, so the underground government allows yakuza organizations to operate because they will be able to suppress danger)