Naoki Kuroi is the younger brother of Tatsuki Kuroi and appears later in the series as a supporting character. He is a fourteen-year-old middle school student who is street-smart, outgoing, and good-hearted at his core. Like his older brother, he considers himself a ladies' man and frequently develops crushes on the girls around him, including Ran Kotobuki, Miyu Yamazaki, Sayo Kotobuki, and, by the end of the television series, Kasumi Tsukino. In the manga version, his affections shift among Ran, Sayo, Miyu, and Aya Hoshino. Naoki is a professional skateboarder and is almost always seen carrying his skateboard, a hobby that often lands him in trouble with the police. Despite his rebellious streak, he harbors a strong sense of family responsibility and regularly helps out at his father's ramen shop. His long-term aspiration is to eventually take over and run the family business. Initially, he is disappointed that his older brother Tatsuki has no interest in inheriting the shop, but Tatsuki encourages him to pursue his own path. Naoki is depicted as cool yet slightly eccentric, much like Tatsuki, and he strives to live up to his brother's legacy. His role in the story is primarily as a comedic and affectionate foil to the main cast, and his development involves learning to balance his youthful bravado with genuine care for those around him.