A tale passed down through the ages speaks of the mermaid's flesh, which grants immortality. Yuta, who lived in Japan 500 years ago, unknowingly consumed a piece of this mystical flesh, extending his life for centuries. However, he yearned to regain his humanity. His search for a mermaid finally bore fruit when he found one, but it revealed a terrible secret; the mermaids kept a young girl as their feed to retain their youthfulness. Yuta put a stop to this, freeing the girl from peril. Although he lamented his actions, he gained a companion in Mana, who spent her life sheltered in a tiny hut, cherishing even the simplest pleasures. Together, they embarked on a mission to locate more mermaids to reverse their transformation into aquatic beings.