Secret agent Maria Wakatuki, codename Blue Cellar Striker, receives a new covert mission. The target is the underground student council of a certain academy, an organization allegedly trafficking female students as "tickling slaves●." Dismissive and annoyed, Maria begins her infiltration, only to find herself plunged into a "tickling hell" that creeps up behind her with silent footsteps. What follows leads inevitably to a "BAD END" conclusion.