"Unlike the other fixers, Kayoko is not one with ill intentions. However, she is often misunderstood as a delinquent simply due to natural scary facial expressions and appearance. She normally prefers to keep silent about this topic, as it likely leads to furthering her terrifying image. From a first glance, Kayoko holds a scary demeanor and is often misunderstood as a troublemaker. In reality, she is a gentle and relaxed individual who goes along with whatever Problem Solver 68 pulls her into. Out of everyone in the club, she is shown to be the most reasonable, calm, and least destructive person as she does not actively seek to cause trouble."

A supporting antagonist of volume 1, I imagine a perfectly reserved, low, and gentle voice for this character, since this is a fandub, feel free to any little quips you feel fit! Will have some lines in the dub. 

Japanese voice reference can be found here: https://bluearchive.wiki/wiki/Kayoko/audio