|Also known as||Aniki (by Ikuya)|
|Age|| 14-15 (High☆Speed!)
19-20 (Free! Take Your Marks!) 20-21 (Free! Dive to the Future)
|Height|| 168 cm (5'6") (High☆Speed!)
185 cm (6'1") (Free! Take Your Marks!)
|Occupation|| Free-lance swim competitor (post-high school)|
|Affiliation|| Soufukan High School (former)|
Iwatobi Junior High School (former)
Unknown elementary school
|Function|| Captain - Iwatobi Junior High School Swim Club (former)|
Bandou Swimming Club (former)
|Swim Style||Freestyle, Individual Medley|
|Events||400m Individual medley|
|Relatives||Ikuya Kirishima (younger brother)|
|Anime||High☆Speed！－Free! Starting Days－|
|Light Novel||Volume 2|
Natsuya Kirishima (桐嶋 夏也 Kirishima Natsuya) is a college-aged individual who competes as a free-lance competitive swimmer following his graduation from high school. He debuts in the second volume of the light novel, High☆Speed！ written by Kouji Ohji and is supporting character in High☆Speed！－Free! Starting Days－, Free!-Take Your Marks- and Free!-Dive to the Future-. He is the older brother of Ikuya Kirishima.
Natsuya is a relatively tall and muscular young man with short, unruly brown hair and amber eyes.
Natsuya is a boisterous, keen, and upbeat character although according to his best friend, Nao Serizawa, he is somewhat socially awkward. On the surface, he doesn't seem deterred by much, but shows a vulnerable side to Nao. He is the Captain of the Iwatobi Junior High School Swim Club and is kind and firm, aspects shown often around his team. He is also highly competitive as seen when first-year team member, Haruka Nanase, claims that he only swims freestyle and the team captain challenges him to a race to determine if this will be so. Their race ends in a tie with Natsuya respecting Haruka's ability, but continuing to monitor and challenge him. Natsuya cares deeply for his younger brother, Ikuya. They are close until Natsuya decides that he must push Ikuya to be less dependent on him. This, while Ikuya is only in elementary school. He distances himself from his sibling without explanation, a move that distresses Ikuya and damages their relationship for several years. Natsuya is an excellent swimmer, capable of earning a living via free-lance racing, which he does following high school. He is also shown to have a low alcohol tolerance.
Natsuya is the captain of the Iwatobi Junior High School Swim Club. His younger brother, Ikuya Kirishima, is also a member of the team. His best friend, Nao Serizawa, is the team manager. Natsuya recruits Haruka Nanase, Makoto Tachibana, Asahi Shiina and his younger brother for the team shortly after they begin their first year of junior high school. Both the light novel and movie titled, High☆Speed！－Free! Starting Days－, depict his tenure as swim club team captain while Season 3 of the anime titled, Free!-Dive to the Future-, depicts Natsuya as a free-lance competitive swimmer after high school.
- Main article: Natsuya Kirishima/Story
Main article: Natsuya Kirishima/Relationships
- Natsuya's least favorite subject is Math.
- His motif animal is a tiger shark.
- He hates shiitake mushrooms but will eat them when he is with Ikuya to set a good example
- His favorite quote is said by Mikhail Makarovich Nitori which is, “Victory only comes to those who believe in themselves,” which he interprets as the results depend on you.