TV-Series
Description
Hii-chan is a mermaid who appears in the anime Muromi-san, where she is introduced as a close acquaintance and self-proclaimed younger sister to the main character, Muromi-san. Her name is derived from the Hii River, continuing the series' pattern of naming its aquatic characters after rivers in Japan.

In terms of personality, Hii-chan is defined by her cheerful and friendly nature, which is expressed using the Hakata dialect, much like Muromi-san. Her most defining trait is her deep and abiding love for all marine mammals, with a specific fondness for whales and dolphins. This affection puts her at odds with Muromi-san, who harbors an intense, long-standing grudge against these creatures due to a romantic betrayal by an aquatic mammal ex-boyfriend in the distant past. While Hii-chan deeply cares for Muromi-san and considers her an older sister, her motivations often center on reconciling Muromi's hatred with her own love for dolphins, leading to comedic conflicts as she tries to prove their good nature.

Within the story's role, Hii-chan functions as a foil to Muromi-san, particularly in episodes that explore the latter's ancient past and irrational biases. Her presence highlights the often nonsensical and exaggerated humor of the series, as her earnest attempts to defend dolphins are met with Muromi's stubborn and explosive anger. The key relationship is unquestionably with Muromi-san; although not biological siblings, their dynamic resembles that of bickering sisters with a strong underlying bond. Other relationships, such as with the human protagonist Takuro Mukojima, are less central to her character. Hii-chan is often seen in the company of the dolphins she loves, which naturally causes her to cross paths with Muromi-san frequently.

Regarding her development within the series, Hii-chan remains a fairly static character, as her primary function is to drive comedic situations rather than to undergo a personal transformation. Her core beliefs and her relationship with Muromi do not significantly evolve, which is consistent with the series' episodic and gag-driven format. In terms of notable abilities, she does not possess any unique powers or skills that distinguish her from other mermaids in the series. Her most prominent feature is a physical one: a headdress crafted from an ammonite fossil, a nod to the ancient age of the characters in the show. Beyond her swimming capabilities as a mermaid, she has no special abilities of note.