Choi is a girl of a petite stature. She has short, jet-black hair with a trinket, and deep magenta eyes. She has a dark skin tone.
Her attire consists that of a traditional, foreign dress as well as neck accessories. She is always barefoot and wears gold anklets and bracelets.
Choi is a normally polite, well-rounded girl, though becomes rather self-contained and withdrawn when she feels suspicion against someone. She is easily embarrassed, and feels mortified when making a small mistake such as confusing Kanna's age to be much younger due to her short stature. She has a tendency to have a need to repay her debts, such as for her gratefulness for the Kitashirakawa family allowing her to reside at their home temporarily, she had cleaned the house and gave fortunes to the market keepers for their kindness.
- Tamako Kitashirakawa: Choi had been initially suspicious and restrained around Tamako, believing Tamako was attempting to "fatten her up" with mochi just like she supposedly did with Dera. She had also rejected her dinner after being mortified by the bathhouse incident. However, Choi soon warmed up to Tamako after the latter had taken care of her when she had a fever, establishing a trusting friendship towards the mochi maker's daughter. Tamako's kindness influenced Choi to believe that Tamako was a suiting bride for Mecha.
- Prince Mecha: She seems to have crush on the Prince and does not refer to him as his first name, but rather, "Prince". She is loyal to him, and is quick to defend him such as when Tamako commented on his young age, pointing out that Mecha is a capable ruler regardless and scolding Dera for treating him rudely. Choi was seen dreaming about him when she was sick, and appears more likely to blush when in his presence. She harbors a strong feeling for the prince.
- Dera Mochimazzi: She is not very fond of Dera, often calling him a useless bird and criticizing how he had gained so much weight from the time he was gone that he had been rendered unable to fly. Dera often teases her. She uses him for augury.
Choi is excellent in augury, capable of telling others of accurate fortunes.
Choi has served the Mochimazzi family for a fairly long time, knowing Mecha since they were children. Despite her surname being the same as Mecha's, she is not related to him. She does not know much of the world outside of her homeland nor their traditions, due to her staying there for so long that she'd contracted a fever in Japan's Usagiyama Shopping District for its different weather.
- Choi's blood type is A.
- In the departure of her and the Prince from the Usagiyama Shopping District, a camera close-up shows Choi touching the choker on her neck, suggesting that she may have "the dark sign"—a marking that she has mentioned all Mochimazzi princesses have.