Mayumi Uchida

A control officer responsible for starboard safety aboard the Harekaza. She is characterized by her somewhat dark complexion.

She has a quiet and gentle personality. However, she dreams of striking it rich and regularly buys lottery tickets within her allowance. Her goal of becoming a Blue Mermaid was actually driven by the desire to travel the world and buy lottery tickets.

She is a childhood friend of Suzu and has previously been dragged into the consequences of Suzu's tendency to run away from things.

In judo, she excels at ground techniques but struggles with standing techniques, which has hindered her progress.