The manager of Musashi FC and Musashi middle school, and later an institute medicine resident together with Jun Misugi.

Personality-wise, Yayoi is a very kind, charming, strong-willed and straight-forward maiden who has also proved herself an optimist, always tried her best in everything she does. As a youngster, she tended to be well-intentioned but quite insensitive to other people's feelings and thoughts; such a flaw was played for laughs when she many times triggered Sanae's jealousy over Tsubasa without even noticing it, and later much more seriously when she asked Tsubasa to let Misugi win and Misugi, once found out, was extremely angry about it.