Iwaizumi Hajime is a powerful and rich mafia leader. He could get anything he wanted, but had this odd Obsession with his 'rival' Oikawa

Oikawa Toru smart, strong next in line to inherit his parents mafia business, but first he'd have to marry the daughter of another mafia to form a permanent alliance to which he agreed

When iwaizumi heard this, he was outraged he was not little his little prince escape. So he kidnapped Oikawas' parents to strick a deal with Oikawa.