In the distant future, a majority of humans have left the Earth, and the Galactic Alliance of Humanity is founded to guide exploration and ensure the prosperity of mankind. However, a significant threat arises in the form of strange creatures called Hideauze, resulting in an interstellar war to prevent humanity's extinction. Ledo, a boy who has known nothing but fighting all his life, saw the sea there for the first time. On its vast, faintly green waters, men organize huge naval fleets and live modest but active lives. Due to language and cultural barriers, Ledo lives as a lonely foreigner... but he's not alone. Ledo is just beginning his days on this green planet, asking what he must do to survive here, and what he is living for.