Tsumugi is a calm and honest half-German girl who decided to use this summer vacation to, "look for things she wants to do". Her personal philosophy is, "Classic books and rules were polished over time to be as rational as possible". Because of that, she even follows rules that clearly don't fit modern society. She is a bit lenient though, and doesn't try to force others to follow those rules. For someone who always talks about rules and logic, whenever she loses a debate, she moans with a mortifying "Mugyu~". Even though she is a calm and collected girl and it feels like she can do anything, sometimes she just blankly stares somewhere or starts talking in monotone. And then there are times when her clothes are frayed like she just rampaged through the mountains. She unexpectedly has a lot of weak points.