Makoto Takashima is a young security guard who's inherited a huge debt from his father. Desperate to pay back his debts – and to buy a proposal ring for his girlfriend Kiyomi – he agrees to do a lucrative job to a yakuza named Masui: stealing a stock prediction AI program from his company. When Makoto tries to extort more money from Masui, Masui kidnaps his little sister Yui. However, nothing is as it initially seems: the AI program is also targeted by a group of professional swindlers, a legendary killer-for-hire, and a young female assassin.