Mai Hanano, descendant of a lineage that has protected the secret ninja arts for over 600 years, continues rigorous ninja training even in the modern Heisei era. But one day, her clan is attacked by rival ninjas seeking the forbidden techniques. Her father is killed, and Mai is forced to suck her brother's cock, suffering humiliating abuse. To extract the secret arts, enemies subject her to relentless torment using the traditional Edo-period Higo Zui-ki technique and modern electric massage devices, transforming her into a lustful beast craving cock. One after another, she swallows dicks and fucks endlessly—what twisted fate awaits Mai in the end?