Two girls named Nana meet on a train to Tokyo. Nana K. aims to reunite with her boyfriend and Nana O. hopes to make it big in the music business. Despite their differences, the pair hit it off and become roommates.
Mitsuki and Yuya become stepsister and stepbrother because of their parents' marriage. Mitsuki can't get along with her new family and Yuya doesn't know how to approach his new stepsister. One day, Mitsuki becomes possessed by the spirit of Hiyori. Hiyori likes Yuya and believes Yuya can help her get to heaven. Hiyori places a leather chastity belt upon on Mitsuki and a plan takes place to help send Hiyori to heaven.
The "Torture Club" is an official after-school activity at the private school Saint Honesty Gakuen. Yuzuki has no idea about the club when she enrolls, and gets abducted by the club members and hauled off the club-room. There, she finds out that upper-class student Aoi, her secret idol, is in the club, and decides to join, but…
