The manga revolves about a mermaid named Muromi, her travels and her quirky personality. She speaks with a Hakata dialect and she thinks sea water fish are better than freshwater fish. She has a sweet tooth and loves sake. She's also said to have been living for thousands of years (although she has the appearance of a teenage girl with a fishtail).

Join Muromi on her adventure, as she gets caught in high school student Takuro Mukojima's fishing nets, as she meets more friends, new and old, and enjoy their weird but hilarious conversations. Or, you could just watch her bother Takuro on his fishing days with lame gags, just for laughs