Chouko Mizushima is the silent protagonist of Persona -3, and the latest wielder of the power of the Wild Card - a blessing that lets her freely switch between Personas in the middle of battle. She represents the Fool Arcana. Her Initial Persona is Eurydice, and her Ultimate Persona is Pantheon.
Chouko's build is surprisingly average, albeit an inch or two shorter than most others her age. Her hair is shoulder-length, light brown, and worn very similarly to the touselled style of the Persona 3 protagonist. Her eyes are chesnut. During school hours, she dresses in the Gekkoukan girls' school uniform, albeit substituting the white dress shirt for a teal pullover hoodie and wearing her blazer unzipped so as to access the pockets of said pullover. She also wears this while exploring Asphodel, as it is the clothing she is most comfortable in despite her being required to wear it by school rules. On weekends and holidays, she wears a teal t-shirt, a denim jacket, and a knee-length skirt.
As a silent protagonist, Chouko's mannerisms are often left up to the player to decide. She can be friendly and supportive, or she can be withdrawn and asocial. Regardless of the player's choices, however, NPCs will often describe her as exerting an aura of kindness that makes her easy to talk to, despite her generally aloof and daydream-like motions. This aura makes her a natural magnet for those seeking advice or companionship.
Her skills are also dependent on the player's choices. She can be an academic genius, or a courageous rebel, or a smooth talker. She can practice a sport, or she can pursue more artistic pastimes. Or she can do all of them and more. It is all dependent on the player.
Due to the nature of the power of the Wild Card, Chouko's Persona is never set in stone. She is capable of using any Persona in the game, with the exceptions of those used by other characters. However, her "Initial" and "Ultimate" Personas are generally considered to be Eurydice and Pantheon.