Chigusa is Gou's friend and also a 1st year student at Iwatobi High School. She is usually seen supporting the Swim Club at their tournaments. She and Gou often hang out together.

Chigusa seems to be a very curious and inquisitive individual, since she cares a lot about Gou's relationship with Haruka, Makoto and Nagisa. She always forgets to address Gou as "Kou", which results in Gou getting upset and correcting her. In addition, she is considerably athletic; she runs much faster than Gou and she often has to stop and wait for Gou to catch up with her.

Gou calls her "Hana-chan."

(Source: Free! Wikia)