Kurumi is a girl who is above average in appearance, athletics, and academics, but who nonetheless suffers from being called plain/boring all the time. If there’s even a hint that somebody has called her plain/boring, she goes off to sulk alone, often in the rabbit cage with Mesousa. She has been known to fade almost completely out of existence altogether when she gets called plain/boring or ignored too much. Kurumi is a very fast sprinter, and also played varsity basketball.
She is the younger twin sister of Shuu Momose of class 1-A who is known for his cooking skills, something that she herself does not possess. Unlike in most anime and manga where the younger sister will call her brother Onii-chan (お兄ちゃん), Kurumi refers to her brother as Aniki (兄貴), which is a much more masculine way of addressing an older brother. It might be due to this that, due to her reactions as seen in episode 20, she has a fascination with how some girls in Japan are now using the pronoun boku (僕), meaning “I”, which is usually only said by Japanese males. It is never explained why she enjoyed this so much. From episode 11 on in the anime, she is shown with her hair grown longer. Additionally, from episode 19 on, she ties her hair in twin braids. She cuts her hair back to its original length for episode 26 and it magically grows throughout its progression.
In later episodes, after experiencing much of the unrealistic events in the first half of the series, she starts to see reality in a whole new light and starts little by little to accept giant fighting robots and small talking animals to be normal occurrences in everyday life. Despite this new outlook at how crazy her life really is, the others always seem to overlook her estranged claims. When not in school, she also has a part time job at a moe café though due to her not being considered moe, business is not as good as the owner would want it to be.