Mai, a university student, has an incredible memory due to an illness she suffered as a child. Her boyfriend Minoru, who noticed Mai's ability to remember everything in an instant, persuades her to use her special ability to play mahjong. Mai is reluctant, but she learns that Minoru has been losing a lot of money at mahjong and is in debt to a man named Akaboshi. Akaboshi sees Mai's ability and suggests that they make some money together.