Sexy Idol Mahjong is, as its title implies, a mahjong game starring popular Japanese female singers and TV personalities. In the game's background plot, they are the so-called "demonic women", ruled by a nearly immortal queen residing in a castle. The player takes the role of a medieval knight who must defeat these women by playing mahjong against them. The player character automatically moves on an overhead map and plays mahjong rounds against the women in a linear fashion. Defeating these opponents may reward the player with their digitized photos, usually featuring scanty clothes and seductive poses.