胡桃和英男之间保持的甜蜜的“Sundome”关系，虽然胡桃无论如何都不允许，英男还是觉得俩人的关系在一点一点靠近。这时，校园里关于胡桃的异性关系的“负面话题”悄悄传播开来，胡桃还因此受到了前辈绘里的大骂…

The high school boy and girl from Sundome 2 continue their sexless relationship in which she is sadistic and he is masochistic, but one day there is a rumour at school about her having a relationship with a different, and older, man. The boyfriend feels as if his girlfriend is hiding her relationship with the older man.

冴えない童貞の高校生・英男は、転校してきたミステリアスな胡桃に一目ぼれし、2人は微妙な恋愛関係を保っていた。そんなある日、胡桃の異性関係にまつわる陰湿な噂が校内でささやかれ始める。