- Shu (?, Sh??)- The owner of a Go salon where Hikaru finds Yuki. Shu knows a cheater when he sees one. He hires Dake-san to teach Mitani a lesson about cheating.
Dake (??, Dake?) - A scam artist hired by Shu to teach Yuki Mitani not to cheat. He poses as a regular at the Go salon and hides his strength. He bets money on the game, reveals his strength, and wins 10,000 yen (about $90 U.S.) from Yuki. Hikaru and Sai later win the money back. Dake sings romantic songs while playing Go as part of his act to appear like a harmless buffoon.
- Heihachi Shindo (?? ??, Shind? Heihachi?) - Hikaru's grandfather, a regional go champion, who owns the board where Hikaru first discovered Sai. He claims his brother bought the board in an antique shop, intrigued by the rumor that a "ghost in a tall hat" would appear from it sometimes. He keeps the board as a memento after his brother's death and refuses to give it to Hikaru, but after seeing how much Hikaru has improved in Go in one year's time, he buys him a nice go board to practice on his own.
- Kuwabara Honinbo (?????, Kuwabara Honinb??) - The current holder of the Honinbo title in Hikaru no Go. Kuwabara is friends with Toya Meijin, but rivals Ogata. He also has an interest in Hikaru and bets on Hikaru in his Beginner Dan series game.
Harumi Ichikawa (?? ??, Ichikawa Harumi?) - Ms. Ichikawa is the cashier of the Go salon owned by the Toyas. She feels saddened when Akira frequents the club less often because of his pro schedule, and in the manga refuses to start calling him "sensei" when he goes pro, preferring to keep calling him by the nickname "Akira-kun." She frequently drives him to different places and he sometimes tutors her in go.