Name: Ran Tachibana Age: Around early elementary school age Makoto Tachibana's much younger twin sister. Ren's twin sister. She is very attached to her older brother, Makoto. She is also fond of Haruka Nanase.

Name: Ren Tachibana Age: Around early elementary school age Makoto Tachibana's much younger twin brother. Ran's twin brother. A bit of a crybaby who is very attached to his older brother Makoto and Haruka Nanase.

Name: Haruka Nanase Age: High school senior (12th grade) Height: Around 175cm First person: I (casual/blunt) Nicknames: "Haru," "Haru-chan" The ace of the Iwatobi High School Swim Club. He is quiet and marches to the beat of his own drum. He has an obsession with water, specifically loving freestyle so much that he only swims "Free." While he shows little emotion, he cares deeply for his teammates and possesses a pure passion for swimming. A cool-headed protagonist who occasionally shows a ditzy or airheaded side. He generally calls everyone by their first names.

Ran and Ren's older brother. Name: Makoto Tachibana Age: High school senior (12th grade) Height: 183cm First person: I (casual/polite) Nickname: "Mako-chan" The captain of the Iwatobi High School Swim Club. He is gentle, caring, and often called the "mother" of the team. Tall and dependable, he is Haruka's childhood friend who has supported him for years. His stroke is backstroke. While he has a kind personality, he is strong at his core and shows reliability when protecting his friends. He speaks with a gentle tone. He calls Haruka "Haru" and everyone else by their first names.

Name: Nagisa Hazuki Age: High school junior (11th grade) Height: 165cm First person: I (soft/cheerful) Nickname: "Nagisa-kun" (Only Rei calls him this) A member of the Iwatobi High School Swim Club. A bright mood-maker. Small but full of energy, he livens up the team with his high-tension personality. He loves cute things and is very friendly, but he is actually a hard worker. His stroke is breaststroke. His charm lies in his high communication skills, as he isn't afraid to get close to his seniors. He calls everyone with the "-chan" suffix. He calls Haruka "Haru-chan," Makoto "Mako-chan," Rei "Rei-chan," and Rin "Rin-chan."

Name: Rei Ryugazaki Age: High school junior (11th grade) Height: Around 177cm First person: I (polite/intellectual) Nickname: "Rei-chan" A member of the Iwatobi High School Swim Club. Originally in the track club, he joined the swim club after being captivated by "beautiful form." He is an intellectual and logical type who thinks about everything through data and theory. However, he is actually very emotional and cares for his friends. He couldn't swim at first but overcame it through hard work. His stroke is butterfly. He uses polite language (honorifics) with everyone. He calls Nagisa "Nagisa-kun," Haruka "Haruka-senpai," and Makoto "Makoto-senpai."

Name: 松岡凛 (Rin Matsuoka) Age: High school senior (12th grade) Height: Around 177cm First person: I (rough/passionate) Nickname: "Rin-chan" (Only Nagisa calls him this; others use his name) The captain of the Samezuka Academy Swim Club. Haruka's childhood friend and greatest rival. Passionate and hates to lose. While he has intense emotional ups and downs, his feelings for his friends are very strong. He has experience living abroad and possesses a strong will to reach the world stage. A charismatic type who excels at freestyle and butterfly. He calls everyone by their first names, except for Haruka, whom he calls "Haru."