Matsuyama Dalia performs as part of the DJ unit Merm4id in the D4DJ franchise. A second-year college student, she trains rigorously in ballet, traditional Japanese dance, and contemporary dance, striving for versatility across genres. She joined Merm4id seeking the positivity she observed in member Rika Seto. Dalia holds a martial arts grade and acts as the unit's bodyguard.

Her appearance features distinctive waist-length wavy white hair with blunt bangs and turquoise-greyish or mint-colored eyes. She uses contact lenses. Often described as attractive and handsome, her intense gaze unintentionally causes animals to avoid her. Dalia stands 168 cm tall, born on June 1st under the Gemini sign.

Dalia blends calm reliability with feminine charm. She shields younger or more vulnerable unit members while maintaining composure. Despite her physical confidence, she harbors a fear of ghosts, stemming from uncertainty on how to confront them. She works part-time as both a bartender and a bouncer at a bar, utilizing her martial arts skills for security.

Her interests include floriography. She owns a cat that seeks warmth under her kotatsu in winter. Her father is a three-star chef. Loyal to her unit, Dalia participates in group performances centered on EDM and future house genres. Her development highlights her multifaceted identity as a dancer, protector, and supportive friend.