Otokichi Shirabe is a supporting character initially presented as a mysterious elderly man frequently seen in Kanon Town's Concert Hall. He dedicates himself to maintaining and completing the hall's large pipe organ, aspiring to play songs of happiness that bring joy to everyone. His signature catchphrase, "It's out of tune!" reflects his deep musical connection and intolerance for disharmony. Residents perceive him as a friendly, eccentric figure with a lovable, old-fashioned demeanor, often riding an antique high-wheel bicycle. He becomes visibly overjoyed discussing his grandchildren, a trait others sometimes use to distract him.

His background reveals significant ties to Major Land. He is Queen Aphrodite's father and grandfather to Ako Shirabe (Cure Muse). After Ako fled Major Land due to Minor Land's invasion, he lived with her in Kanon Town, expressing immense affection. Otokichi possesses knowledge of interdimensional travel between Earth and Major Land and demonstrates music-linked abilities, such as creating a rainbow-colored piano by clapping his hands. Playing this piano allows him to shoot keys that trap targets within barriers. He knows the Legendary Score, the Melody of Happiness, and the Melody of Sorrow, understanding the pipe organ's completion is vital to prevent impending disaster. He is also aware of the Pretty Cure team's identities and artifacts like the Crescendo Tone.

His involvement progresses throughout the story. He first appears overhearing Kanade and Hibiki talking to Hummy, displaying skepticism about their excuses. Forgetting a doll resembling himself at the hall leads to an episode-long chase as the girls attempt its return. Later, he repairs the town clock after Negatone infection, an act coinciding with Cure Muse's first appearance that aids the Cures against the Trio the Minor. While the Cures gather scattered notes, he plays the Melody of Happiness on the pipe organ, helping them defeat a Negatone and attracting numerous stray notes, creating mystery around his melody knowledge. He later appears in Major Land, revealing his travel ability, and persuades Aphrodite against going to the human world during Mephisto's attack. His knowledge proves crucial; he deduces Mephisto is controlled by the Noise of Evil and recognizes Pii-chan's true identity as Noise.

His name carries musical significance: "Shirabe" relates to "tone" or "playing music," while "Otokichi" combines "sound" and "joy" or "good luck." He wears blue glasses adorned with F-clef symbols, hinting at his Major Land origins. His character embodies themes of music and protection, acting as a guardian figure whose eccentric behavior masks his profound role in safeguarding harmony across worlds.