Siren Senki

A huge immigrant ship "Antilia" from the earth flew to the water planet Siren, and started to invade the whole of Siren, starting with the undersea city-state "Amoroth".

Amoroth's guard captain Spalt, whose king and lover were slaughtered, advocated a total resistance and encouraged his subordinates to fight back, but they were helpless and defeated, swearing revenge and leaving their homeland.

…Thus, the battle between the earthlings and the aquatic humans of Siren over the planet Siren has begun.