Aiichirō Nitori is a supporting character in the Free! series, a student at Samezuka Academy known for its competitive swimming club. He has short gray hair with straight bangs, light blue eyes, and a distinctive teardrop-shaped mole or beauty mark located diagonally under his right eye. His height is recorded as 168 centimeters during his early high school years, later increasing to 171 centimeters. He is friendly, earnest, and hardworking, though he can be a bit of a chatterbox who sometimes speaks without thinking. His deep admiration for Rin Matsuoka is the central motivation of his character, originating from an elementary school tournament where he was deeply moved after watching Rin and his teammates compete in a relay. He looks up to Rin as a mentor and role model, striving to become strong enough to swim alongside him on the Samezuka relay team. This admiration leads him to emulate Rin, including attempting to specialize in both freestyle and breaststroke. Despite being aware of his own limitations as a swimmer and sometimes struggling with self-doubt, he is persistent and refuses to give up, pushing himself to extremes in training. His role in the story is often as a supportive underclassman and conversation partner for Rin, helping to draw out Rin’s thoughts and feelings. He receives crucial guidance from senior Sosuke Yamazaki, who coaches him in the breaststroke and encourages him not to deny his own possibilities. Through hard work, he improves his times, breaks a school record, and earns a spot on the relay team, fulfilling his dream of competing with Rin. He also becomes close friends with his roommate Momotaro Mikoshiba, despite their contrasting personalities. It is revealed that his uncle is Mikhail Makarovich Nitori, an Australian swimming coach who mentors Rin. By the end of his third year, Rin appoints Aiichirō as captain of the Samezuka Swimming Club, a testament to his growth and reliability. Outside of swimming, his hobbies include playing with dogs, and his favorite food is borscht.