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- Main article: Haruka Nanase
Goro used to be Haruka's coach while he was still a coach at Iwatobi Swimming Club. When Rin came back from Australia during his Middle School years, Goro was the one to let him and Haruka race back at the Iwatobi Swimming Club pool. He was the only one to know about Rin's and Haruka's race and Rin's breakdown up until he talks with Makoto one night after running into him. He cares for Haruka and others very much and is willing to give his all to help them improve their swimming.
- Main article: Makoto Tachibana
Goro used to be Makoto's coach while he was still a coach at Iwatobi Swimming Club. One night, wanting to visit the abandoned swim club building, Makoto ran into Goro, but didn't recognize him. After having a talk with him (not knowing it was actually Goro), he recognized him as Coach Sasabe and told him that he was one of his students. Goro then, realising it was Makoto, noted that he grew big.
- Main article: Nagisa Hazuki
- Main article: Miho Amakata
The two seem to know each other from the time when Miho worked as an office lady, but when Goro asked her if he knew her from somewhere, she denied claiming that she met him for the first time.
Later it is found out that Miho used to be a swimsuit model, and the reason Goro felt like he had met her before was because he had seen her in several magazines and was a big fan of hers. However, he was forced to keep quiet about this and never bring the topic up again.
- Main article: Rin Matsuoka