The mother of Moritaka Mashiro and sister-in-law to Nobuhiro Mashiro. She is initially against her son becoming a mangaka.
Kayoko is the mother of Moritaka Mashiro and the husband of Mashiro, whose name and face are never actually seen throughout the series. Not much is revealed about her past but she does feel strongly about how Mashiro's life should be. She thinks that he should spend less time goofing around and study more to get into a top school and get a high class job as opposed to leading the life of a mangaka. As much as she hates the idea of seeing her son pursue the same path as her brother-in-law Nobuhiro, she still supports him as a son.
Kayoko Mashiro was created by Tsugumi Ohba and Takeshi Obata to be the standard parental figure in Mashiro's life. In a sense, she is the first real roadblock on his path to becoming a mangaka since she wants her son to become successful as a standard Japanese man. She makes her first appearance in both the beginning of the manga and the anime.