Fifteen-year-old Choco Mitsumata, born Chiyoko, is a first-year high school student radiating cheerfulness and energy, often serving as her group's mood maker. Her appearance features twin long braids secured by orange bows, and she wears glasses daily. Her typical outfit pairs a collared white dress shirt beneath a multicolored striped short-sleeved shirt, a blue pleated skirt, white leg warmers, and brown loafers, accessorized with an orange bracelet and red circular earrings. Her witch attire includes a yellow and black short kimono with a red ribbon and yellow flower layered over a white shirt, long socks adorned with yellow lines, a white hat featuring a yellow stripe, and yellow kimono shoes.

Despite her positive exterior, Choco frequently succumbs to unexpected dozing spells caused by exhaustion from her significant responsibilities. Following her father's death during her childhood, her mother, a nurse often absent due to night shifts, became the sole provider. As the eldest, Choco shoulders substantial caregiving duties for her grandmother, who has dementia, and her younger siblings, Yayoi and Taizo, classifying her as a "young carer." She secretly uses time-rewinding magic to manage these demands alongside her activities, inadvertently deepening her fatigue and leading to zoning out during tasks or conversations. She hides these struggles to avoid pity.

Her character journey centers on Episode 7, where her concealed burdens erupt publicly. During a birthday celebration, she reacts harshly to her grandmother's dementia-related behavior, shocking friends and straining her bond with Kyōka Kitahara, who disapproves of Choco's perceived irresponsibility. This prompts intervention, leading Choco to accept assistance from friends like Yuina Akagi and institutional support. By confronting her challenges and utilizing these resources, she gradually lessens her caregiving load, reconciles with Kyōka, and adopts healthier coping strategies.

Choco enjoys watching baseball and sewing, favors foods like curry, yakisoba bread, and sweets, and dislikes celery. She frequently exclaims her energetic catchphrase, "Choco-chan Cutter!" Her experiences underscore themes of youth caregiving and mental health.