Gou Matsuoka  

Kou, 松岡 江

Rins younger sister is named Gou and attends Iwatobi High School as a first-year student. She possesses an easygoing personality, but constantly worries about her brother, Rin. As the manager of the Swim Club at Iwatobi High School, alongside Haruka, Makoto, Nagisa, and Rei, Gou aims to help change Rins behavior back to its previous state. Gou is highly efficient and supportive in her role as the clubs manager, devising training routines for the team, sourcing practice partners, and gathering information on opposing teams. She prefers not to be addressed by her real name, Gou, opting instead to be called "Kou" (same kanji reading). Despite this preference, Nagisa consistently calls her by her real name. Gou has a muscle fetish, blushing around men when admiring their physiques. However, she eventually gives up on this interest due to Nagis persistent calling of her by her real name.