Season
Episodes
Spring Begins
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.
Insects Awaken
Convinced that Botan has kidnapped them, Natsu and Arashi sneak out of camp and run into another survivor. Finally, Botan reveals what she knows.
Light Snow
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.
Autumn Begins
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.
Heavy Snow
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.
Grain Rain
Aramaki joins Team Spring, despite Fujiko's doubts. Hana decides to search for Arashi after hearing that Aramaki met someone who fits his description.
Winter Solstice
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.
Summer Solstice
Hana's group and the Team Autumn survivors find the Spring settlement destroyed and abandoned. Momotaro wakes up among strangers.
Lesser Heat
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.
Cold Dew
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.
Greater Heat
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.
End of Heat
Ryo orders Hana to join him in searching for a water source underground, putting her in a vulnerable position. In the caves, Ango recalls Shigeru.
Frost Descends
Team Summer A banishes Ango and Ryo as Haru and the others mourn the missing Hana. Aramaki leaves the settlement believing she is still alive.
Summer Begins
Expecting a trap, Ango and Ryo find and observe Team Summer B, but they are unexpectedly welcomed by the easygoing group.
Grain in Ear
The two newcomers help Team Summer B. As they get to know the group, Ryo doubts their ability to survive. Ango begins to see Natsu as Shigeru.
Autumnal Equinox
The carefree group enjoys life at sea, but Ryo tests their survival skills. Natsu reveals that Team Summer B is for dropouts, angering Ango.
Vernal Equinox
Suspicious, Botan searches Ryo and Ango's belongings while the others look for Arashi. Elsewhere, another survivor learns about the wilderness.
White Dew
Team Summer B gets stuck in a bed of dense algae. they find a large ship and investigate, but Botan is wary. Stranded, Arashi sees the ship's kite.
Winter Begins
The team members are separated after the ship's sudden movement. Arashi makes his way to help as Botan's group makes a discovery.
Lesser Cold
Ango's hallucinations lead to perilous situations for him and Arashi. Semimaru has a brush with death while Natsu gathers her courage.
Grain Full
A sanctuary in nature becomes a trap for small mammals and humans alike. Meanwhile, an iron-eating bacteria begins to spread throughout the ship.
Rain Water
Fujiko and Chisa reunite with Hana. On the ship, the missiles begin launch prep while Team Summer B learns about Ango's past and the test.
Greater Cold
Hana readjusts to other humans. Team Summer B works together to manually disable the missiles, but a series of passcodes complicates the process.
Pure Brightness
Problems persist in the ship as the spreading bacteria begins attacking. The missile countdown continues as the team makes a mad dash to exit.
Cast
Nao Toyama
Natsu Iwashimizu (voice)
Jun Fukuyama
Arashi Aota (voice)
Katsuyuki Konishi
Semimaru Asai (voice)
Kana Asumi
Matsuri Tendou (voice)
Kazuhiko Inoue
Kaname Mozunoto (voice)
Akira Ishida
Chimaki Yamori (voice)
Yoko Hikasa
Hana Suguruno (voice)
Hirofumi Nojima
Haru Yukima (voice)
Shizuka Itoh
Fujiko Amacha (voice)
Kenta Miyake
Akio Haza (voice)