Nagi and Shizuka's former assassin training institution, "Gakuen," is pursued by the siblings Kurosaka Naozumi and Touko, who arrive on Guichen Island. The A-class students suspect that the numerous "strange killings" occurring on the island are Nagi's doing and begin their search. Shizuka encounters her former classmates, Naozumi and Touko, who press her for Nagi's whereabouts, putting her in a life-or-death situation.
