Umi is a remarkably kind, gentle, and radiant woman. She was not born in Endera but in the neighboring country of Lumeria, having immigrated to Endera only recently. Because of her recent arrival, she missed most of the news surrounding the emergence of Tiny Disease. Furthermore, the Enderan government has gone to great lengths to suppress coverage of Tiny Rights Movement (T.R.M.) protests and incidents, leaving Umi completely unaware that tiny people even exist beneath her feet.

As a result, she goes about her daily life without the slightest suspicion. Thanks to the extraordinary elasticity and resilience of tiny bodies, they simply compress and flatten beneath the soles of her shoes without her feeling anything at all, regardless of how many are caught underneath. Despite possessing one of the kindest hearts imaginable, Umi unknowingly leaves chaos and tragedy in her wake every time she walks through the city.
She once mentioned to a friend that she had noticed strange stains regularly appearing on the bottoms of her shoes. Her friend merely laughed and replied, "Don't worry. It's just dirt from our filthy streets."

Embarrassed for bringing up something so trivial, Umi never mentioned it again. After all, dirty shoe soles hardly seemed worth worrying about when there were so many more important things in life.