Mrs. Usui, Fumio's mother, was not seen in the anime nor mentioned, but in the manga she was said to be abusive to her daughter when she got pregnant with Kenta when she was sixteen which caused her to drop out of school. While she demanded Fumio to get an abortion her daughter refused and she was physically abusive with her daughter in hopes she would miscarry but her attempts failed. When her grandson was born she constantly called him a monster for his eyes and was always angry and unhappy.Not wanting her son to get hurt anymore, Fumio and her son ran away to the city to start a new life, disowning her mother. It is unknown what her reaction was or if she cared. At the end of the manga when she got sick, Fumio came to take care of her, though it is unknown if she felt remorse for how she treated her daughter and grandson or apologized to either of them for her behavior.
- She has been described as someone who NEEDS to abuse others.