English teacher Mizuhara Sana is suddenly attacked and kidnapped while walking down a dark street, dragged into a deep darkness and completely overtaken. Bound tightly with restraints, she undergoes merciless training that allows no resistance. Her anus is forcibly stretched and developed, until eventually she swallows even the toys she once rejected. Awakening to pleasure, she begins craving cock and reaches climax through two intense double penetrations. Her ecstasy deepens further as repeated anal creampies become a new source of pleasure. Ultimately, after taking in twelve loads of cum, Mizuhara Sana is fully transformed into a sex slave.