Reiko, who was left alone for the rest of her life after her husband's sudden death, moved into the house where her late husband's sisters Misuzu and Ayaka lived. The sisters welcomed Reiko warmly as if they were their own family, but Reiko is perplexed by the sexual behavior of the two, which can be taken as abnormal. One night, Reiko, who saw two sisters devour each other's bodies, was driven by a lust she had never felt before and ended up masturbating alone. With that as an opportunity, Reiko was absorbed in a lewd world that only women could know.
