Misuzu Ooyama is a supporting character in the anime Darker than Black: Kuro no Keiyakusha. She is an elderly woman who serves as the landlady of the apartment building where the protagonist Hei resides in Tokyo. She is married to Toshiro Ooyama, though he does not appear prominently in the series. Misuzu has grey hair that is tied up at the back of her head with a decorative pin featuring a red ball, and she has dark-colored eyes.

Her role in the story is primarily that of a mundane, everyday presence in Hei’s life. She provides him with normal human interaction and a stable place to live, contrasting with the dangerous and mysterious world of Contractors and espionage that Hei navigates. She is not involved in the supernatural or political conflicts of the series and has no special abilities. Her personality is straightforward and no-nonsense; she frequently chases away the cat-like character Mao, who attempts to enter the building. This behavior suggests a practical, somewhat stern attitude toward keeping order in her property.

Misuzu’s motivations are limited to her duties as a landlady—managing her building and dealing with tenants. She does not undergo any significant character development throughout the series, remaining a static background figure. Her key relationship is with Hei, whom she treats as an ordinary tenant, unaware of his true identity as a Contractor. This unawareness highlights the disconnect between Hei’s violent secret life and his need for a normal cover. Misuzu Ooyama represents the ordinary world that Hei tries to protect and the everyday routines that anchor him despite his extraordinary circumstances.