The protagonist leads an ordinary school life. One day, he wakes up to a familiar voice and a weight between his legs. They are two sisters from a neighbor's house who moved in a few years ago.

He is fidgeting with his morning situation, which is peculiar to boys. One of the sister's sits on top of him and presses her crotch against his and stimulates his son! She dares him to cum.

And so began the daily life with these innocent, mischievous sisters.

“Don't you want to do something more pleasurable? We've been practicing for you for a long time, haven't we?”

The protagonist, who doesn't understand the meaning, is forced to take off his pants, and ends up getting double-fucked again without any resistance. In fact, the sisters are in a battle of sex.

“The one who makes him feel better gets to be big brother's girlfriend!"

What will happen to the protagonist in this sudden and unexpected turn of events?

[From official site]