Shū Iura, a student in Class 3-2 at Katagiri Senior High School, stands 172 cm tall with distinctive green hair and matching green eyes, often seen in a sweatshirt and purple headphones. At school, he bounds with extreme energy, loudly initiating pranks and group activities. His constant chatter and boisterousness earn him an "annoying" reputation, with classmates comparing him to a hyperactive green ball of energy. This talkative nature is seen as a barrier to romance, with the suggestion that more girls might like him if he were quieter. He acknowledges his identity is inseparable from this energy, questioning what would remain without it. He shares a deep friendship with Tooru Ishikawa, stemming from elementary and middle school, bonding over activities like exchanging music. His loud attempts to connect with classmate Honoka Sawada, however, only make her avoid him. At home, Shū adopts a starkly different persona: subdued, serious, and cold towards his younger sister, Motoko Iura. Their relationship features frequent arguments and physical confrontations, leading Motoko to initially mistake his sternness for hatred. Despite this outward demeanor, he harbors deep concern for Motoko's well-being and academics. He recruits Kyōko Hori to tutor her for high school entrance exams and threatens physical retaliation against a teacher who mocks Motoko's efforts. He secretly buys her a good luck charm for the exams. His protectiveness extends to scrutinizing Motoko's friend, Aoi Kitahara, who develops feelings for him, though he remains oblivious or unresponsive to her admiration. Within his class, Shū forms friendships, including one with Izumi Miyamura, sharing music collections—a bond established before Miyamura's appearance change. He is part of the core friend group including Kyōko Hori and Yuki Yoshikawa. A past relationship with a similarly energetic girl ended in breakup, leaving him sensitive during discussions about romance. Shū created the segment "Let's try asking Iura-kun!" where he posed questions to others and formed the "Katagiri 6" group. He named himself "Katagiri Green" due to his hair color, a nickname others also use for him.