"The world we used to know is fading away, and all we can do is watch it happen."

Japan has fallen and most of its population has died at the hands of a pandemic.

Yamada Daisuke and Fujiwara Sayaka have settled at the southern end of Japan, in Kagoshima. The former office worker and former high school student stick together, doing their best to survive the winter. But without modern inventions, even the mild winter of the south is a challenge to weather.

But staying in one place feels like a shame, so the two of them decide to travel all the way to the northernmost part of Japan - Hokkaido. Get there by summer and return to Kagoshima before the winter.

All around them, the Japan they used to know is fading away. What will they find in these remains?