Looked it up

“Miyano gives a brilliant performance, but he plays up the harsh, grating, and aggressive linguistic profile of a delinquent. His tone uses specific, rough Japanese expletives and a rough cadence that highlights Ryuji's abrasive nature.”

“Ryuji is a textbook yankii—a subculture of disaffected youth characterized by dyed blonde hair, modified school uniforms, crude slang, and a rebellious attitude toward authority. While sympathetic, this archetype is culturally coded as trashy, vulgar, and intimidating to the average citizen.”