In an era where the earth is desolate and massive vessels traverse the boundless seas, a singular breed of sub-human, known as the mermaid, emerges. Typically, their hair is white, but once submerged in water, their locks transform in hue. The wealthy trade these rarities amongst themselves for extravagant prices. Hisui, sporting distinctive scarlet tresses, serves as a merman under the guardianship of a nobleman. Nevertheless, his fate takes a turn when he is abducted by the pirate, Ikuta and embraced by newfound liberation, commences an adventure beside his captor.
