Yutori Chikuzen

筑前 優鳥, Trick or Treatment

Chikuzen, along with the other members of the Plus Six, are unknown to Maguro Kurokami, indicating that they did not become a part of the Flask Plan until after he left. She is a senior of Class 13 and a former member of the Flask Plan's Plus Six.

Ten years later, Chikuzen is a hairdresser.

(Source: Medaka Box Wikia)