Ako Shirabe, also known as Cure Muse, is the tritagonist of *Suite Pretty Cure♪*. As the Princess of Major Land, she fled her kingdom after its takeover by Minor Land and now resides in Kanon Town with her maternal grandfather, Otokichi Shirabe, while attending Municipal Kanon Elementary School as a third-year student. Her parents are Queen Aphrodite of Major Land and King Mephisto, who serves Minor Land under brainwashing.

Initially presenting as reserved, abrasive, and arrogant, Ako frequently lectures others, especially protagonists Hibiki Hojo and Kanade Minamino, displaying brutal honesty. This behavior stems from her belief that she alone must save Major Land without help, a burden resulting from her kingdom's fall. Her civilian appearance features orange eyes, short orange bob-style hair, and magenta rectangular glasses. She typically wears a pink long-sleeved shirt under light indigo overalls with cerise buttons, magenta socks, and white sneakers with light blue details.

Ako's hidden alter ego is Cure Muse, initially concealed as the Masked Pretty Cure. This disguised form presents an older appearance due to platform heels and a full-body black outfit with a turtleneck, cape, and a heart-gem-adorned mask. Her eyes shift to magenta, and her Fairy Tone partner, Dodory, speaks for her, maintaining an aloof and mysterious demeanor. As the Masked Cure, she aids the Pretty Cures using barriers and restraints formed from colorful piano keys while insisting she is not their ally. Her true Cure Muse form, revealed in episode 35, features bright orange knee-length hair with yellow ribbons, magenta eyes, a yellow blouse with a shawl, a golden choker, and a ruffled balloon skirt. Her transformation phrase is "Playing the Goddess' tune, Cure Muse!" (爪弾くは女神の調べ！キュアミューズ！).

Ako became Cure Muse the day Mephisto stole Major Land's Legendary Score, hiding her identity to avoid confronting her father. When Mephisto targets the Cures in episode 35, she reveals herself as his daughter and cures his brainwashing with a punch, restoring his true self. Following this, she fully joins the team, shedding her cold exterior to reveal her true nature: a sweet, music-loving girl who enjoys singing and exhibits maturity beyond her age. Despite her royal status, she rejects formal titles, insisting on being called by her name.

In the movie *Suite Pretty Cure♪: Take it back! The Miraculous Melody that Connects Hearts!*, Ako gains the Crescendo Cure Muse upgrade. This form grants her large wings, lighter curled hair, and a white-and-yellow outfit with cape-like feather details. Her attacks include Shining Circle and Sparkling Shower, executed using her Cure Module and secondary Fairy Tone Shiry. She also participates in team finishers like Suite Session Ensemble Crescendo.

Ako shares a close bond with Souta Minamino (Kanade's brother), whom she treats sternly but considers her best human friend. Souta briefly harbors implied romantic feelings for her, though she remains unaware. Her relationships with her family are pivotal; she adores her mother Aphrodite and initially becomes a Cure to save her father, though she occasionally finds his behavior awkward.

Key trivia includes:
- At age nine, she is the youngest Pretty Cure in the franchise.
- She is the first elementary-school-aged Cure and the first fourth member with a yellow theme (though her Masked form uses black).
- Her surname "Shirabe" means "tone" or "playing music," while "Ako" derives from "acoustic."
- She is the only *Suite* Cure without a dedicated weapon, relying on Fairy Tones for attacks.