As night arrives the shadows of Koga fall on Iga and a new threat exists for our lusty vixens. After a torid sexual encounter Yatsurugi Shinobu's best friend Mashiba Aya is infected with a parasitic bug and succumbs to its will. Having the same insatiable urges, the same tragedy is about to happen to Kage Lena. The only known antidote is stored deep within the labs of the Koga Institute and is the only thing which will save Kage Lena.