Mafia Stepbrothers

Bangtan's dad get married to a woman who have a young daughter.

Bangtan being mafia king of underworld hiding their mafia identity by being business mafias for real world.

YN being a young girl gone through disturb family and unsuccessful and unhappy love life.

Bangtan agreed to accept their dad's marriage for his happiness but not the daughter and yn also accept her mom's marriage for her happiness but is unsure about her stepbrothers.