Kentaro Habara is a recurring character in Boogiepop and Others, known primarily as a talented hacker and a close ally to Nagi Kirima. He is a high school student who has spent much of his academic career using his technical skills to infiltrate the computer systems of various companies and sell the stolen data on the black market. He engaged in these activities without any sense of remorse, viewing the security lapses of his targets as their own fault and his actions as a consequence of their negligence.

His path crossed with Nagi Kirima when she intervened to save him from being caught by the authorities during one of his hacking attempts. Nagi installed a virus on his computer that alerted him to police surveillance, allowing him to avoid arrest. After this event, he met Nagi in person and quickly developed a deep, one-sided romantic infatuation with her. His primary motivation became supporting her, and he began to assist her with her missions and investigations.

Kentaro has a personality that is notably more outgoing than his childhood friend, Shirou Tanaka. Despite his background as a solitary hacker, he is socially confident and has been shown laughing openly at others, a behavior Shirou would try to temper. He holds his friendship with Shirou in high regard, admitting that he considers Shirou to be more reliable than himself and is grateful for their long-standing bond, which dates back to elementary school.

His role in the story is largely that of a supportive figure working behind the scenes. Using his hacking abilities, he assists Nagi in gathering information and locating targets, such as when he helped find a building where a girl named Kit was being held captive. He desires a more active, hands-on role in the dangerous situations they face, wanting to prove his worth and capabilities to Nagi. However, she often restrains him from direct participation, not out of a lack of faith in his abilities, but out of fear that he might be killed or seriously injured. Kentaro frequently misinterprets this caution as Nagi underestimating him, which drives him to attempt solving incidents on his own to demonstrate his value to her.

During the King of Distortion arc, Kentaro becomes one of the main characters trapped inside the mysterious Moon Temple. There, he is confronted by the titular entity, which manifests within his psyche by taking the form of Nagi Kirima. This psychological encounter forces him to confront his feelings and desires regarding her. Following the events of this incident, he acquires resources and information inherited from Kyouichirou Teratsuki, the creator of the Moon Temple. He uses these new tools to continue his intelligence-gathering activities in support of Nagi's ongoing battles against the Towa Organization. In later stories, he uses the code name Sidekick to disguise himself while posing as an agent of the Towa Organization. His most notable and consistently demonstrated ability is his expertise in hacking and computer-based information gathering. In the anime adaptation, he is a tall young man with slicked-back, spiky black hair and black eyes, typically dressed in casual clothing like a black letterman jacket over a red t-shirt and blue jeans.