Mero is a mermaid from a fantasy world who travels to Earth, becoming one of the supporting characters in the series. She works at a fish market called Gamu Fisheries, where she sells seafood. To maintain a human form on land, Mero drinks a Maca supplement, which allows her to grow legs and walk among humans. In her true form, she is a merrow, a type of mermaid, with blue hair and blue eyes.

Mero has an extremely energetic and cheerful personality. She speaks in an affected Kansai dialect, which she uses to sound more friendly and approachable. Her great passions are karaoke and eating fish, and she often eats fish three meals a day. Because she no longer swims as much as she did in her original world, her upper arms have become flabby from muscular atrophy, a side effect of her sedentary modern lifestyle. This weight gain around her arms is a point of concern for her, but she maintains a positive and carefree attitude.

Her primary motivation is to enjoy life on Earth, exploring human culture, food, and daily activities. She is curious about everything new and quickly embraces local customs, especially those involving food and entertainment. Her role in the story is as a supporting character who interacts with the main cast, offering comic relief and a lighthearted perspective. She forms friendly relationships with other otherworldly visitors and the human characters who help them, particularly around the fish market and during group activities. While she does not undergo dramatic character development, she adapts steadily to human life, learning to balance her merfolk nature with her new environment.

Mero's notable ability is her transformation from a mermaid into a humanoid form using the Maca supplement; without it, she would require water to survive. In the water, she retains her mermaid tail and natural swimming ability. On land, her energetic nature and love for singing make her a lively presence in any group.