Masumi Okuyama is a supporting character in the anime Ajin, depicted as an Ajin who operates as a member of Sato’s group. He is born with a weak right leg, a physical limitation that does not hinder his expertise with weapons and computers. Okuyama’s background prior to joining Sato is not extensively detailed, but his skills suggest a background in technical or combat-related fields. He is motivated by an allegiance to Sato’s cause, participating in the larger conflict between Ajin and human authorities without a deeply explored personal agenda. Within the story, Okuyama serves as a capable operative, leveraging his technical knowledge and combat proficiency to support Sato’s operations. His key relationships are primarily within Sato’s faction, where he functions as a reliable subordinate. Okuyama experiences limited development throughout the narrative; he remains a consistent figure focused on his duties, and his character does not undergo significant transformation. His notable abilities include immortality, which is common to all Ajin, and exceptional control over his invisible black matter (IBM), which he commands precisely and obeys his orders. His IBM is described as having a skinny appearance. Okuyama’s competence with firearms and computers makes him a versatile asset, compensating for his physical weakness. Overall, he is a technically skilled and loyal enforcer within the Ajin underground.