It was a summer mistake... Five years ago, Michiko came to our house as my father's new wife. At first, it was a little awkward, but before we knew it, we had become a natural family thanks to Michiko's devoted kindness. Then, one day, my younger brother Tetsuya told me something I couldn't believe. "Mom invited me to do something naughty..." After hearing that story, I started to think of Michiko as a woman. Then, noticing my gaze, Michiko also cast a mysterious gaze at me...