■ Synopsis

The protagonist, Terumi, is living his high school life to the fullest — he has many friends and even casual partners. However, he has an older sister who is completely unlike him. They live in a single-mother household, and while their mother works hard, his sister voluntarily handles all the housework.

However, she lacks confidence, is timid and quiet, doesn’t wear makeup, and her hair is always messy. She hides her constantly warm body shape in oversized, baggy clothing year-round. She is a female college student like this. There is a reason she turned out this way — but the protagonist has no way of knowing it.

One day, the two of them unexpectedly run into each other in the changing room. The body that had always been strictly hidden is suddenly exposed before his eyes — this happened during one humid summer day. From that moment on, their relationship begins to change significantly.

And what was hidden was not just her body. The emotions swirling inside her silent heart — feelings that a normal person could never understand — are still unknown to him.

■ Chapter Two

At last, the sister and brother become intimately connected. However, the protagonist, unable to do anything against his sister — who possesses what he imagines to be the ultimate level of “skills” — ends up only releasing semen, and begins striving to overcome his premature ejaculation.

A beautiful woman at his part-time job watches him closely, waiting for him to reach the age of consent. There is also a trap hidden within the temptations of a girl who let her adolescence run wild. And then, an astonishing change begins to occur in his sister’s body...

After overcoming numerous hardships (and pleasures), will the protagonist finally be able to make his sister experience intense pleasure with his large manhood?

■ Chapter Three

The protagonist, a complete scumbag, is surrounded by two beautiful lovers. Just when he was dreaming of happy days, he learns that a photo of his “my son” wildly scattering semen has been leaked.

That girl who, for some reason, eats breakfast at the Shimizu household. The shocking sexual desires of his lover are revealed. His beloved sister, whose every hole has become like a sexual organ, begins working a part-time job. And then… his heart wavers due to the great feelings hidden within her small body.

— Is this divine punishment…?

Author's Note:

It is not guaranteed that this will unfold exactly as written. This is a self-imposed reminder to properly outline the story before writing it.