Abyss Azure no Zainin  

A Sinner of the Deep Sea, Sinner of the Azure Abyss, Sinner in The Seabed, アビスアジュールの罪人

An epic fantasy that portrays the forbidden romance between mermaids and humans. The oceans cover approximately 70% of Earth's surface, concealing a world unknown to humanity. Deep beneath the waves lies a submerged nation, thousands of meters below the surface. Joe, a mermaid living peacefully there, faces a dilemma when her best friend Ryuu is imprisoned for violating the law that prohibits humans from knowing about their existence. What are the reasons behind this rule? Who is the other human involved? To rescue her beloved and embark on an adventure, Joe's journey begins.