Marika Mizushima possesses light brown hair often swept into a high side ponytail and distinctive lavender eyes. Born July 30 in Tokyo, she stands 162 cm tall, weighs 50 kg, and has blood type O. As a Seiho University student, she balances academics with an active modeling career, inspiring peers like Towa Hanamaki. Her family comprises unnamed parents, an older sister, and a grandmother.

Despite her popularity, Marika maintains an easy-going, calm, and down-to-earth demeanor. Initially perceived as too busy for friendships at university due to her modeling commitments, she formed a profound bond after Rika Seto approached her unreservedly—a connection Marika deeply cherishes. While generally relaxed, she exhibits intense passion for concerts and DJ activities, though she dislikes insects and admits poor cleaning skills.

Her hobbies include café visits and creative nail art. She savors fluffy foods like pancakes but avoids salted plums, despite occasional attempts to eat them. Her theme color is neon green.

Within DJ group Merm4id, Marika serves as a dancer. She embraced DJing seriously after Rika’s invitation, performing in a signature outfit: yellow flower hairpieces, a white shoulderless crop top with yellow accents, blue denim shorts, a golden wrap, and black heels. Preparing for events like "D4 FES.," she collaborates with Saori Hidaka and Dalia Matsuyama, attentively noting Rika’s behavioral shifts during rehearsals to navigate group dynamics.

Her visual design influenced other media, notably inspiring characters like Ninon in the unrelated Eve Bots project.