On a winter day with the north wind blowing, I was left feeling the warmth of kotatsu and my aunt.

This winter, when it started snowing, I dropped out of university, and was taught to study for the qualification exam at my friend's mother, Sanae (Shiraki Yuko). My crotch was on the verge of explosion as I was alone with Sanae and the kotatsu, which I admired. That day, I was glued to Sanae's thighs peeking out from the kotatsu, and I couldn't get a chance to study for qualifications. When Sanae realized that she teased her legs as if to tease her. What's more, Sanae's prank wouldn't end there...