As night cloaks the villages of Iga and Koga, a shadowy threat stirs against the academy's elite female operatives. After a charged encounter, Yatsurugi Shinobu's closest friend Mashiba Aya is overtaken by a parasitic organism that bends her to its influence. The same affliction now endangers Kage Lena, compelling Shinobu to race toward the Koga Institute in search of the sole antidote that can reverse the condition before it claims another victim.
