A shy girl named Natsu learns that she’s part of a group chosen to ensure the survival of humanity. Together, they have to survive on a changed Earth.

1. Spring Begins 25m Along with three others, Natsu wakes up with no idea what's happened. The four of them reach an island and try to figure out a way to survive.

2. Insects Awaken 24m Convinced that Botan has kidnapped them, Natsu and Arashi sneak out of camp and run into another survivor. Finally, Botan reveals what she knows.

3. Light Snow 24m Natsu's clumsiness indirectly leads Team Summer B to the rest of their group. Her memories help them figure out their location, and their next moves.

4. Autumn Begins 26m Arashi, Natsu and Semimaru stumble upon the Team Autumn settlement in the former Kobe region. They seem to be thriving, but their leaders are tyrants.

5. Heavy Snow 25m In the ruins of Tokyo, Natsu, Arashi and Semimaru meet the sole survivor of Team Winter. Team Spring reaches Mt. Ogino Fuji and finds Natsu's message.

6. Grain Rain 26m Aramaki joins Team Spring, despite Fujiko's doubts. Hana decides to search for Arashi after hearing that Aramaki met someone who fits his description.

7. Winter Solstice 32m Hana and her companions discover a massive underground shelter. They find a survivor’s diary and learn the cruel fate of those who took refuge there.

8. Summer Solstice 24m Hana's group and the Team Autumn survivors find the Spring settlement destroyed and abandoned. Momotaro wakes up among strangers.

9. Lesser Heat 25m To survive, Hana and the others work together with Team Summer A. On the ship, Hotaru's cousin Hibari tells Natsu that Hotaru is slowly dying.

10. Cold Dew 26m Ango recalls his harsh upbringing in the program and the brutal graduation test that winnowed the survivors down to the final Team Summer A members.

11. Greater Heat 24m Hana becomes convinced that Ango will kill her if she stays in the village. Natsu and the others make landfall near the former Autumn settlement.