Saeki Yumi

She lives alone with Yuki in an apartment. After her husband died, she never remarried and raised Yuki alone. She has kept her family name as it is. Her husband is the younger brother of Akira's father.

She works for a company, but it is unclear what it is. However, Akira has seen her go to work during the weekdays. She is usually dressed very casually. She is young and does not look like a mother.

She is kind to Akira because he looks just like her late husband when he was young. She is a little happy to have an adorable son in her daily life as a single mother. She provides all kinds of service to Akira.