|Also known as||Nao-senpai|
|Age||14-15 (High☆Speed！ Vol. 2)|
19-20 (Free!-Take your Marks-)
(Tokyo Swimming Club; former)
|Anime||High☆Speed！－Free! Starting Days－|
|Light Novel||Volume 2|
Nao Serizawa (芹沢 尚 Serizawa Nao) debuts in the second volume of the light novel, High☆Speed！, written by Kouji Ohji. He is a supporting character in High☆Speed！－Free! Starting Days－, Free!-Take Your Marks- and Free!-Dive to the Future-. His first interaction in the series is seen when he is co-captain and manager of the Iwatobi Junior High Swimming Club, playing an instrumental role in the development of the team comprised of Haruka Nanase, Makoto Tachibana, Ikuya Kirishima and Asahi Shiina. He currently lives in Tokyo where he studies Sports Medicine at Oudoukan University.
Nao is tall with an average, but toned build. He has long gray hair with bangs, yellowish-green eyes of a droopy nature and is usually seen wearing a kind expression. Since graduating junior high school, he wears eyeglasses and his hair is shorter.
Nao is a gentle, patient, and soft-spoken individual with keen insight into the motives of others and a logical approach to life. His empathetic nature helps him to motivate the students he coaches, as seen when he works with Haruka and his teammates, identifying their individual obstacles to improvement, then helping each one develop for themselves a strategy to overcome them. Though unable to swim since his eye surgery, his tolerant nature has allowed him to channel any frustration he may feel into coaching and pursuing his goal of entering the field of Sports Medicine. He is a loyal friend to Natsuya Kirishima.
- Main article: Nao Serizawa/Story
Nao is a third-year at Iwatobi Junior High School when Makoto and Haruka enter as first-years. He is the co-captain of the school's swimming club and president of the library committee, as revealed in the light novel. In High☆Speed！－Free! Starting Days－ it is revealed that he goes through an eye surgery.
In Free!-Take Your Marks-, Natsuya says he doesn't swim due to said injury; adding that he wishes they could swim swim together again, someday, but must wait until Nao is medically permitted to do so. Nao goes on to attend Soufukan High School, graduating and moving to Tokyo, where he studies sports medicine at Oudoukan University. In an ironic twist, he is the previous owner of the Tokyo apartment in which Haruka currently lives.
- Main article: Nao Serizawa/Relationships
- Before getting into swimming, he was into Aikido (a form of martial arts).
- He is the coach of Misaki Kuramoto in Free!-Take Your Marks-.
- His motif animal is a northern gannett.
- Nao keeps tropical fish in an aquarium at home and one of his hobbies is looking after them. The other one is watching movies/documentaries with Natsuya.