Momoko Asuka is a Japanese girl who moved to New York at a young age because of her parents' work. This early relocation led to significant language and cultural adaptation challenges upon her return to Japan, as she had forgotten most Japanese. This resulted in initial shyness and social withdrawal. She gradually overcame these barriers through friendships with Doremi Harukaze and others, revealing her fundamentally energetic, optimistic, and enthusiastic nature. In New York, she formed a close bond with the witch Majomonroe, who mentored her in baking and English. This relationship ended tragically when Majomonroe fell ill and died. Grief-stricken, Momoko attempted forbidden magic to revive her, which failed and resulted in the permanent loss of her witch powers. The Witch Queen later granted her a second chance at witchcraft, recognizing her potential value in supporting other witch apprentices.

Physically, Momoko is the tallest among her peers. She possesses fair skin, distinctive lime-green eyes lacking visible pupils, and long chartreuse hair typically styled in looped braids secured by lavender accessories and a cyan clip. Her standard attire includes a cropped orange shirt, a white skirt featuring a yellow corner split, yellow suspenders fastened with cyan buttons, black socks, and white sneakers with yellow laces. Before returning to Japan, she wore cyan sneakers. Her design incorporates a signature three-leaf clover motif, reflected in her witch accessories.

As a witch apprentice, Momoko uses transformation spells like "Pretty Witch Momoko-cchi!" and casting spells such as "Perutan Petton Pararira Pon!" Her magical stage invocation is "Perutan Petton, Sawayaka ni!" Her fairy companion is Nini, and her chartreuse crystal ball takes the form of a three-leaf clover. She initially obtained her magical abilities under Majomonroe's guidance, only to have them revoked after the forbidden resurrection attempt. Upon rejoining the witch apprentices in Japan, she contributed to operating a magical sweets shop, where her baking skills became central to group activities.

Personality-wise, Momoko demonstrates high intelligence, academic diligence, and strong passions for reading, studying, and sports. She exhibits occasional goofiness, emotional expressiveness, and a strong advocacy for peace and individual freedom. Though generally good-natured, she can display stubbornness and prefers to avoid confrontation. When overexcited or stressed, she often lapses into English. Her development shows increased confidence and social integration, though she retains moments of nostalgia for her life abroad.

Her relationships evolve significantly. Initially, her bluntness accidentally hurt Hazuki Fujiwara and Onpu Segawa, but sincere apologies led to strong friendships. She shares a particularly close bond with Doremi due to their similar energetic dispositions and shared classroom experiences. With Hazuki, she bonds over mutual fears of horror stories. Her relationship with the magical baby Hana began strained after she unintentionally made Hana ill, but she worked diligently to rebuild trust and later expressed disappointment when Hana altered their bakery-themed shop.

In later narratives, including light novels, Momoko focuses on culinary training with aspirations to reopen Majomonroe's New York bakery. She attends a specialized baking school and participates in activities like cheerleading. Her family includes her father Kenzou, an architect often working abroad (such as in China), and her mother Minori, a fashion photographer, contributing to her transnational experiences.

Key trivia notes her birthday (May 6), blood type (AB), favorite color (yellow), and instrument (guitar). Her name combines "Asuka" (flying bird) and "Momoko" (peach child). She shares a Japanese voice actress with the character Masaru Yada.