ChaO.

In a futuristic world where humans and mermaids coexist, the life of mild-mannered office worker Stephan is upended when he is suddenly proposed to by Chao — a princess from the mermaid kingdom. With no time to make sense of what's happening, Stephan soon finds himself living with the unpredictable, wholehearted Chao, and her sincere love begins to break down his emotional barriers.