Kuroiwa operates as a talent agent at Iris Talent Agency, managing pop star Yuki Kano. He participates in coercing protagonist Bosujima into accepting a case by orchestrating the killing of Bosujima's dog, an intimidation tactic forcing compliance. This action establishes his involvement in the agency's ruthless methods.

Later revelations expose Kuroiwa's hidden affiliations: he is an undercover agent for Japanese intelligence services. His placement within the talent agency served as cover to infiltrate and investigate a dangerous religious cult connected to Yuki and her family. This dual role positions him as a triple agent navigating between the cult, the agency, and his intelligence duties.

During the final confrontation at the cult's headquarters, Kuroiwa accompanies Bosujima and actively participates in the violent conflict against cult members. His role shifts to providing critical narrative exposition, revealing key background: the cult leader is Yuki's mother, aiming to transfer her psychokinetic powers to Yuki for succession, while Yuki's stage manager father intends to betray the leader and seize those powers. This information clarifies the central familial conflict driving Yuki's turmoil.

Following the destruction caused by Yuki's unleashed powers, which kill her father and demolish the cult building, Kuroiwa survives alongside Bosujima and Yuki. He later intervenes to eliminate a surviving cult assassin armed with projectile needles, preventing the assassin from killing Bosujima during the aftermath.

His background prior to infiltration, specific motivations for intelligence work, and fate beyond the OVA events remain undefined. His character functions primarily within the conspiracy plot surrounding Yuki's condition and the cult.