斎藤 千和 - Saitō Chiwa
She attended Assam military school along with Rygart, Hodr and Zess. She was known as the "Mad Scientist" for secluding herself in the school's lab for up to 3 days and nights at a time without eating or drinking.
She pursues a career of science and cares deeply for her friends, to the point of pointing a gun at Rygart upon first seeing him to ask why he didn't show up at her wedding and confirm that he does not hate her.
While she is the Queen, she rarely acts like one as she usually spends her time in the castle maintenance workshop tinkering with machines alongside the royal engineers. While she and Hodr are married, they both sleep in separate chambers suggesting their union was an arranged marriage.
It is later revealed that Sigyn was in love with Rygart during their days in military school but Rygart purposely didn't hear her confession to him when he returned to take over his father's farm.
Rygart felt Sigyn deserved a better life with someone else. Even after her marriage to Hodr, she still loves Rygart.