Becoming Obedient to a Gloomy Pipsqueak's Huge Dick

The protagonist was once cheerful and popular... but as time passed, perhaps due to his naturally small stature, his personality became gloomy, and he became isolated in his class. Adding to his troubles was Takana Megumi, a childhood friend who went to the same school. Although they were close as children, at school, she avoided him, as if hiding their past friendship, and wouldn't even speak to him. But one day, Takana Megumi called him behind the school building and asked him to "show her your dick"...