- Shigeo Morishita (?? ??, Morishita Shigeo?), also known as Morishita Sensei or Mr. Morishita - A 9-dan pro who is Waya's go teacher and leader of the study group which Hikaru also frequents on Waya's invitation. He considers Toya Meijin a rival, since the two of them became pros at the same time. Morishita also mentors Michio Shirakawa (7-dan), the community Go leader.
- Mitani's sister (????, Mitani no Ane?) / Yuki's Older Sister - A girl who works at an internet cafe and lets Hikaru play go on the computers for free during her shifts. She also helps Hikaru with his English. The name used to describe Yuki's sister is different in the English version since Yuki Mitani is usually called by his given name, "Yuki", in the English versions. In the Japanese versions Yuki is referred to by his family name, "Mitani" - therefore his sister is called "Mitani's sister" in the Japanese versions.
- Suyong Hong (Hong Su-yeong, ? ??) - A Korean Go professional, 2 years younger than Hikaru. He is 12 when he first appears in the manga. Hikaru, Waya, and Isumi travel to go salons to sharpen their skills while they are insei. In one of them they meet Su-Young, whose uncle runs a go salon, while Su-Young is on vacation from Korea. At the time, Su-Young is a Kenkyuusei (the Korean equivalent of an insei), but is disillusioned with playing Go. Heated words between him and Hikaru lead to the two playing an incredible match at the Go salon. Hikaru beats Su-Young and this spurs Su-Young to work harder to become a pro. Su-Young becomes famous after beating a 9-dan in Korea. He appears again in the manga as the third representative for Korea in the Hokuto Cup.
- Seiji Ogata (?? ??, Ogata Seiji,?, 10-dan) - A Go professional who recognizes Hikaru's talent when he explains a go move during a children's tournament that even professional Go players would take some time to see. He is also a student of Koyo Toya and soon takes the Judan and Gosei titles when Koyo Toya retires. His birthday is January 17. He is obsessed with fish and smokes often.