Yuuko Kinoshita, older than her twin brother Hideyoshi by three minutes, serves as Class Ambassador for Fumizuki Academy's Class 2-A. She ranks within the year's top ten students academically, a stark contrast to Hideyoshi's position in Class 2-F. While sharing her brother's brown hair and green eyes, Yuuko distinguishes herself with two navy blue hair pins anchoring locks on her left side and the standard female uniform: a white and red shirt, red tie, and skirt. Hideyoshi wears the male uniform and sports one hair pin on each side. Their personalities diverge significantly; Yuuko is prideful, easily agitated, and frequently critical of Class 2-F, viewing them as the school's academic disgrace. She directs particular frustration toward Hideyoshi for his association with the class, often projecting her disappointment in him onto all of 2-F. Her personal interests include reading yaoi novels.

Her summon is clad in heavy armor and wields a jousting lance, with an occult variant resembling a Bakeneko. Yuuko harbors a deep grudge against Class 2-F stemming from a Summoner Test War incident. During this event, 2-F tricked Hideyoshi into impersonating her to provoke other classes, leading to a battle where a collapsing bell caused Yuuko to fall through a roof. She later reemerged to defeat Yuuji Sakamoto’s summon, securing victory for Class 2-A, an act which solidified her resentment towards her brother and his classmates.

Yuuko exhibits competitiveness with Hideyoshi outside academics, acknowledging his superiority in areas like singing and rhythm where she lacks skill. She once coerced him into swapping identities to film an academy promotional video, leveraging her intimidating demeanor to force his compliance, revealing her insecurity in his areas of talent and her willingness to use aggression to mask it. She maintains a close association with Shouko Kirishima, Class 2-A’s representative, often aligning with her during school conflicts.