The story follows Ria, a former guitarist for the disbanded pop band Brain Drain, who now works at a supermarket as a single mother. Despite leaving her rock dreams behind, she has never given up hope of forming a new band. Her life changes when she meets a girl named Maria, who possesses what Ria believes is the perfect voice for the rock band she envisions. Beyond their shared passion for music, the two discover they share the same kanji characters for Maria in their names.

Set in contemporary Japan, the manga explores the chance encounter between these two kindred spirits. The title group, Maria's, is formed around the duo as they pursue rock stardom against the backdrop of everyday adult responsibilities.

The first major arc involves Ria struggling to balance her mundane job and single motherhood with her rekindled musical ambition. Maria enters as a catalyst, pushing Ria to confront her past with Brain Drain and the reasons for the band's dissolution. Subsequent narrative threads focus on recruiting additional members and overcoming the obstacles of age, finances, and personal history to make the band a reality. The series highlights the contrast between the raw energy of rock and roll and the practical limitations of adult life.