Cha-Komon, born Aria, is a spirited feline who roams Yumegaoka High School under the principal’s ownership while forging bonds with students—particularly the Diving Club. Hikari Kohinata dubbed him "Cha-Komon" for his distinctive "cha" vocalizations and chairo-tipped ears and tail, a name that stuck after their first meeting. Though initially mistaken for a stray, he shadows the club loyally, even joining their off-campus excursions.

His life shifts when Ohime, a rescued kitten, arrives. Cha appoints himself her steadfast guardian, balancing playful antics with a knightly devotion to her safety. His sleek frame, marked by snowy fur, coffee-brown ears, a striped tail, and piercing blue eyes, contrasts with his drooping ears’ gentle charm. Fearlessly sociable, he perches on shoulders or heads, radiating friendliness despite his ironic distaste for water—a humorous foil to the club’s aquatic pursuits.

Linked to Kozue Amano’s legacy, Cha’s original name echoes a feline from the *Aria* series, while his nickname honors Amano’s real-life pet. Though his narrative remains steady across media, his enduring presence cements him as the club’s mascot, embodying warmth and camaraderie through every whisker-twitch and purr.