Takumi just cannot stop fantasizing about Saki-senpai, her voluptuous body just stands out anywhere. One day she talks to him on the train and they become friends. Whenever he can, Takumi stares at her form, always getting a hard-on. The next day he finds out they have the same fetish... and so the story begins.
A young student has a strong attraction to his stepsister so he constantly keeps looking at her, but she always seems to despite him, so he finds a relief in his 2 swiming class teachers, he like one the most and he always idolizes her not knowing that she is in fact as lewd or even more that himself, so when the teachers discover his stalking habit decide to punish him in some ways he never expected. After that finally he gets to know that his sister in fact feels the same for him so they decide to be honest with their mutual love.