Touhai: Ura Rate Mahjong Touhai Roku

Ever since moving into his own apartment, quiet high school student Kei has been looking for a new thrill. He soon finds himself playing mahjong, but his whole life takes a dramatic turn when he is forced to play the game with a criminal group. Even though the odds seem against him, Kei is able to outmatch the others. Instead of claiming his reward in cash, however, he decides to take an abducted girl named Amina under his wing.

Due to Kei's skills and cold playstyle, the mysterious Hideharu Seki takes an interest in him, introducing him to mahjong parlors and new potential opponents. But when matched up against an experienced player named Doujima, Kei is severely outskilled and only narrowly escapes going into serious debt. If he wants to protect his new life with Amina, Kei must find a way to outwit these shady characters and come out on top in every game he plays.