Yakumo Saotome, the eighth Saotome sister, serves as a Valkyrie dispatched to Midgard under Odin's command, tasked with defending it from demonic threats. Her name, meaning "eight clouds," reflects her birth order. Petite at 145 cm tall, she possesses distinctive short light-blue hair and blue eyes. In human form, she constantly wears headphones to manage her hypersensitive hearing, a necessity for her auditory abilities. Transforming into her Valkyrie state reveals a dark-blue uniform adorned with golden accents, featuring an open back and topped with a visored cap. She wields the holy sword "The Sound," a weapon capable of amplifying the holy sword powers of her sisters.

Her personality blends apparent coldness, sharpness, and laziness, largely stemming from her auditory sensitivity. Noisy environments cause discomfort, and losing her headphones triggers significant distress. Despite this reserved exterior, a playful and occasionally sadistic streak emerges, particularly during teasing or perverse scenarios. Her interactions with Takuma Akutsu, the Einherjar assigned to strengthen Valkyries through emotional bonds, are frequently antagonistic. She openly expresses irritation towards him, primarily because her ability to hear his constantly pounding heartbeat proves intensely grating, highlighting her low tolerance for sensory overload rather than malice.

As the Valkyrie of Sound, her role centers on auditory manipulation and support. Her Seidr ability grants superhuman hearing, making her acutely aware of environmental sounds and physiological cues like heartbeats. This power provides strategic advantages in battle, where she leverages sound-based enhancements for her sisters' holy swords. While she exhibits initial reluctance and an abrasive attitude towards collaborative missions, her long-term development within the broader narrative and specific personal history beyond her assignment to Midgard remain defined solely by her identity as one of the Saotome Valkyries.