Kokoro was dating her boyfriend in the third grade, but she secretly had feelings for Yuki, who was on the same baseball team as her boyfriend. In the midst of all this, I started my managerial duties. One summer day, Kokoro was cleaning up the rooftop alone after a club activity when he was suddenly hit by a guerrilla downpour. The door from the rooftop to the school building is locked. - Kokoro has no choice but to enter the club room, and then she finds herself in an unexpected situation alone with Yuki, who was also left behind. While the signal of the mobile phone is weak and it is difficult to contact the outside, two people in a small space ... Young men and women were piling up their bodies in uncomfortable humidity.