July 2013, in Japan, the cruelest summer since Heian era called "Fierce Heat of a Thousand Years" was attacking the land, giving remarkable temperature rise in all over Japan.
Hiromi Kato, a second-year high school student who lived in a suburb with their parents, were being writhed by the heat of "tropical night" in their room without an air-con. Then, Hiromi got a phone call from Moriyama, their classmate. Moriyama told Hiromi that the supplementary lesson during the summer vacation had been rescheduled.
The next day, Hiromi unintentionally took a nap on the couch after the breakfast since they could barely sleep after the phone call because of the heat. A few hours later, as Hiromi woke up having difficulty of breathing, they realized the room was bizarrely hot. Then, the days of unusualness and danger began under the blazing sun...