Aion, the lion Myumon and lead guitarist of ShinganCrimsonZ, carries himself with a regal demeanor, often posing with one hand covering his mouth during speech—a gesture tied to an implied communication disorder. He proclaims himself "The Dark Sun God" or "Black Monster," embracing darkness and self-declared divinity. His guitar, "Holy Ark," displays chains in its Myumon form and bears a chaos-like symbol.

Standing 195 cm tall, he has a pale gray lion physique, crimson eyes, and a white mane, typically clad in black or purple trench coats, pants, and boots. In demon form, his eyes gain intricate black sclera, and he dons a red-gradient cape adorned with bat motifs. As Scarlet Eye of Darkness, the cape shifts to purple with additional bats, one masked.

Aloof yet attention-seeking, Aion frequently mumbles to himself. He avoids sunlight and outdoor environments, favoring darkness. Despite his intimidating presence, he exhibits fierce loyalty to bandmates Crow, Yaiba, and Rom, shares a close bond with his younger sister Ailane, and maintains a committed relationship with Nepeta.

His history includes resisting dark-monster transformation through bandmate intervention. Across conflicts, he battles intergalactic threats like Queen Victorious and Bud Virgin Logic, aiding ShinganCrimsonZ’s defense of Midi City and the Sound Universe. Musical passion and talent anchor his character, with his poses and performances integral to his identity.