Ku Fei, a Chinese exchange student in Mahora Academy’s class 3-A, combines martial arts mastery with an infectious energy. Her striking appearance—darker skin, blonde hair, and a muscular 151 cm frame—sets her apart, as does her Japanese speech peppered with an "aru" suffix, a linguistic quirk contributing to her academic struggles and role as "Baka Yellow" in the remedial study group. Born March 16, 1989, she specializes in Xingyi Quan and Bagua Zhang, wielding ki control instead of magic, securing her status as Mahora’s top non-magical fighter despite ranking fourth overall in combat prowess.

Renowned for effortlessly repelling daily challengers, her pre-series victory in the academy’s martial arts tournament cements her reputation. As Negi Springfield’s mentor "Ku Rōshi," she hones his ki manipulation and close-combat skills, pivotal for overcoming Evangeline’s trials. A mishap during the Kyoto trip sees her forging a flawed Pactio contract via a paper clone after joining a kiss contest, exposing both her loyalty and romantic naivety.

Her bond with Chao Lingshen thrives through shared heritage and shifts at Chao’s food cart, where nikuman dumplings fuel their camaraderie. Chao’s secret time-travel mission strains their friendship, culminating in tearful farewells. At the Mahora Festival, Ku Fei triumphs over Mana Tatsumiya in a tournament, sustaining a broken arm later healed by Albireo Imma, and confronts Chachamaru clones during Chao’s uprising.

Separated from Negi’s group in the Magical World, she sharpens her skills as a mercenary, shattering stone pillars bare-handed before reuniting with enhanced ki mastery. Spin-offs like *Kuro Arashi: The Black Storm* maintain her prominence, while fleeting references to descendants like Alysia Fei hint at a legacy unexplored in the core narrative.