Satoru is introduced as a deeply traumatized child, exhibiting minimal emotional expression while fixated on repetitive television viewing. His ability to perceive others' inner thoughts manifests horrifically when he witnesses his mother's graphic suicidal ideation visualized as dismembered body parts and despair-filled imagery, causing him to scream and inflict self-harm by banging his head against objects. Hospitalized following such an episode, he encounters Hayashi, who intervenes psychically by transporting him to a calming meadow with a rainbow—later revealed as Hayashi's "Peak," a mental sanctuary housing one's most treasured memories. This intervention enables Satoru to form stable memories and communicate.

Physically, Satoru possesses short, bleached blond hair (sometimes dyed black for missions), upward-slanting eyebrows, and small hazel eyes. A prominent vertical scar on his forehead, self-inflicted during childhood trauma, becomes a trademark feature. His appearance includes multiple facial piercings: one on his left eyebrow, one nostril piercing, and four helix piercings on each ear. He typically wears casual attire, such as a gray zippered vest with purple accents over a long-sleeved black shirt, gray pants with purple details, and strapped boots.

Satoru's psychic ability centers on memory manipulation using a door as his primary "image"—a mental construct facilitating entry into others' subconscious. He specializes in navigating "Peaks" and "Valleys" (representing cherished and suppressed memories, respectively) to alter perceptions or erase memories. His work often involves coordinating with other psychic operatives. For instance, he assists Katsuragi in extracting information by synchronizing their entries into a target's mind, though he cautions against simultaneous threats and mental synchronization due to the risks of becoming trapped in hostile "Valleys." When confined under surveillance, he demonstrates resourcefulness by turning a hotel maid into a "carrier pigeon"—a person covertly manipulated using keywords to bypass monitoring—showcasing his adherence to Hayashi's teachings about evading the Company's watch.

His relationships define key aspects of his development. Hayashi, his rescuer and surrogate father, raised him for a decade, imparting crucial survival skills and knowledge about the Company's surveillance. Satoru remains unaware that Hayashi concealed his status as a Company employee and shared his Peak with others. His devotion turns to vengeful fury upon falsely learning that Hiroki caused Hayashi's mental destruction ("crushing"). Initially, he works pragmatically with Katsuragi, accepting their morally ambiguous missions despite privately expressing pity for targets. He later prefers collaborating with Jin, a fellow psychic, finding her more engaging than Katsuragi. Interactions with Hiroki begin supportively, such as visiting his pet store to alleviate loneliness during Hayashi's absence, but deteriorate into hostility after Tsukasa's deception about Hiroki's role in Hayashi's crushing. This culminates in a violent psychic confrontation where Satoru traps Hiroki's goldfish image and later manipulates him into perceiving Satoru as Tsukasa to facilitate an escape abroad.

Satoru's character arc transitions from a detached operative to an emotionally driven avenger. His calm demeanor fractures upon believing Hiroki betrayed Hayashi, revealing a capacity for intense rage. This shift peaks when he bleeds heavily from a leg injury and hijacks Hiroki's memories to access critical information on a memory drive. Though he initially withholds erasing Hiroki's memories of Tsukasa to avoid causing further harm, his actions underscore his unresolved trauma and the cyclical nature of manipulation within the Company's influence.