Haru Kurabayashi, also known as Hal Kurabayashi (a Westernized rendering of Haru), is a new investigator at Japan's Bureau of Health and Welfare Narcotics Control Department in the Kanto region. Partnered with Kai Etō, they form a central investigative duo. Professionally designated as a "matori" (narcotics criminal investigator), Kurabayashi earns recognition as the "brilliant new investigator" within the Drug Enforcement Division for his exceptional competence, marked by intense focus and dedication.

He maintains a stoic, reserved, and outwardly detached demeanor, yet demonstrates significant protectiveness toward Etō. This bond stems from their shared history: Kurabayashi's father used hypnotic techniques to suppress Etō's violent alter ego and traumatic childhood memories following the murder of Etō's parents. Kurabayashi strategically leverages his notable charm and physical attractiveness during investigations to gather intelligence from diverse sources.

His highly regarded professional skills emphasize analytical thinking and effectiveness against drug-related crimes. Together, Kurabayashi and Etō investigate dealers, gangs, and the powerful trafficking organization Ryuugen. Their cases gradually unravel the truth behind Etō's dissociative episodes ("switching") and their intertwined pasts, particularly concerning the mysterious drug "Switch." Kurabayashi navigates this complex history while sustaining his partnership with Etō amid escalating dangers and revelations.

The character appears in the original manga series and its two-part OVA adaptations released in 2008 and 2009.