Saeko and Yukako live together in a small apartment complex in Tokyo. After the Tohoku earthquake in 2011, both live in a state of unease. Saeko, who is in a divorce, is worried that her daughter is exposed to radiation. Yukako is also afraid of radiation and tries to convince her husband to move. The two become friends after Yukako tries to save Saeko after a suicide attempt.
A decade after his heroic defeat of the monstrous Kraken, Perseus-the demigod son of Zeus-is attempting to live a quieter life as a village fisherman and the sole parent to his 10-year old son, Helius.
When an evil spirit known as Pitch lays down the gauntlet to take over the world, the immortal Guardians must join forces for the first time to protect the hopes, beliefs and imagination of children all over the world.