Yuiko is Riki's classmate who has a self-sufficient personality. She is sometimes seen carrying a replica of a katana. She is seen as an older sister to everyone despite being the same age of almost the entire cast, and is referred to as Anego (姉御, "elder sister") by Haruka. She is fond of things or people she considers to be cute, such as several of the female cast of characters. She gets high grades in school and is especially gifted in mathematics. She was born outside of Japan, but is still entirely Japanese. She was given the birth name of Elizabeth which would often be shortened to Lizbeth as a nickname but does not share this as she prefers to be referred as Kurugaya.
