One day, Mukoujima Takurou, a boy in high school who loves fishing, catches a pig tailed mermaid called Muromi-san who speaks in the Hakata dialect. She comes to visit Takurou often, along with her fellow mermaids Sumida-san, Fuji-san, Levia-san, Hii-chan, and even some other fantastical creatures such as Yeti and Harpy!

(Source: Crunchyroll)