"When my eyes were open, I vividly remember seeing my sister and only my sister. We were playing together on the beach, and splashing water at each other. We were laughing, smiling. We were there for each other. We were with each other. We were-happy. Then darkness took over. 

When my eyes opened again, my sister was gone. So was the beach, and when I looked down-I had a tail."

 

Attel Silva finds herself, awakening in a hospital after getting sucked into a suspicious whirlpool in the ocean. The first thing she discovered when she became conscious again, was that her legs had been surgically removed and replaced by a tail. A mermaid's tail.

Trapped in an underwater world, The realm of Silune, anger and despair fill her when she's thrown into an internment camp with humans who have gone through the same surgery as herself.

Since then, escaping and returning to her sister have been her only goal, it didn't matter how she achieved it.

Yet considering her ranking and class in the underwater world, there are moments when even she can't help but question if finding a way out is even a possibility.