A teacher at Sumiyuri Private Academy and saviour of Ichihime Yukariki: Yuma Shisei. She was previously known as ZigZag, a failed string user. After saving Ichihime, Yuma taught her how to become a string user as well, in order to help others. Yuma is kind, as she helped save twelve year old Ichihime while working with Jun Aikawa. Beyond that, not much is known.

Spoiler

It is notable that Yuma did make Ichihime promise to never use ZigZag in a harmful way, though that later failed when the academy found out.

Spoiler

Ichihime uses ZigZag as an alias when meeting Ii, though she directs the alias to an unknown person to not bring suspicion upon herself. When mentioning ZigZag, however, when written in katakana it refers to Ichihime, while if it's written in kanji, it refers to Yuma.