Kurokuma has a gangster-like, obscene personality. He swears often and has an impatient, immature nature. He is very immoral and has a rather dark, vulgar sense of humor. Some of his jokes are references and more clever, while others are simply immature or just bizarre.

He is also very brash and disrespectful, even towards people he just met. He isn't above cheap insults or provoking. He appears to enjoy annoying Nagisa Shingetsu the most, most likely because of the boy's strict personality.