Mifuyu is a light-skinned girl with periwinkle-colored eyes, rosy cheeks, and dark brown hair. Some of her hair is tied into a small ponytail with a purple scrunchie.
For her winter attire, Mifuyu wears a blue coat with a large, baby pink section on the center, and blue pants.
For her snowboarding or competition attire, she has a yellow headband around her forehead, and protective goggles that are attached. Mifuyu has a purple coat with a connected white jersey. The jersey has red, thin sections in each sleeve and prints the number 11 on the center. Mifuyu wears white gloves with small, blue sections on half, and light yellow pants.
Mifuyu is a snowboarder and handles the techniques very well, but whenever someone shows expectations from her, she becomes nervous and runs for the hills (literally). She's just a kid in an adult snowboarder situation.
She is met by Kukai Souma, Amu Hinamori, Tadase Hotori, and Nadeshiko Fujisaki in Episodes 14 and 15. The Guardians are on a 5th and 6th grade snowoarding field trip. Mifuyu is supposed to teach them. She appears out of a snowman, and is seen making talk and friends of Amu early on.
When some contestants in a snowboarding practice tell her that they are expecting her to do her best in the snowboarding competition, she becomes so nervous that she boards away from everyone. Amu sees this and starts to follow her, wondering what the problem is.
Just then, Amu's Guardian Characters sense the presence of her Heart's Egg and go after her, and when they arrive her egg appears and hatches. In order to help her understand what a Guardian Character is, Amu explains to her and introduces her Guardian Characters.
Because her strong heart made a strong Guardian Character, Yuu Nikaidou chooses her Guardian Character to be his target of making an Embryo. By making her insecure again, she loses her confidence and Snoppe becomes an X-Character. However, Amu is able to save Snoppe and helps Mifuyu in the competition, where she wins the first prize.
Mifuyu's Guardian Character is a small, eskimo-like guardian named Snoppe, whose egg she gave birth to after she begged for herself to not be nervous when people expect things from her.
When she undergoes Character Change with Snoppe, she becomes calm and is able to give snowboarding her best shot without feeling the pressure of other people's expectations. As an aspect of the change, a snowflake hairclip replaces her headband.