This summer is different from previous ones, not only the temparature but also my mind and body. Shintaro has a beautiful mother and pretty younger sister who have been living with him. But this summer is somehow different.... One day, when he enters a bathroom to have a bath, there is a sister, Tomoe. She gives a shriek and runs away. This is the first time for him to see his sister as a woman. And when he soaks in a bath, Tomoe comes in to apologize for what she did to him and she says she will wash his back....