70% of the world is ocean. That 70% has become humanity's enemy.

70% of the Earth is ocean. That 70% is ruled by "Meijuu" (Demon Beasts). Meijuu suddenly appeared in oceans all over the world, making it impossible for humanity to advance into the oceans and severing diplomatic relations between countries. Meanwhile, humanity boards submarines to attack the Meijuu, holding on to a glimmer of hope. Ven cannot give up his longing for the "blue sea" that his brother told him about as a child, and boards the submarine "Steer" as a Meijuu observer.

What color will the sea reflect in Ven's eyes?

A maritime battle fantasy about reclaiming the sea!