射落 ミズキ

“There is a possibility that it's just a prank, or a joke. In any case the present culprit is.... that unsettling man.”

A person of unknown gender who possess androgynous features and is the oldest member of the group. 
In contrast to their cool appearance they're quite lively.
They are in charge of keeping everyone in order. 
Along with the Parallel Universe Broadcasts, Mizuki's gender is the number one mystery among the group.