Tatsuhiko Kadowaki (門脇龍彦 Kadowaki Tatsuhiko) - Kadowaki is a former Go champion who won the collegiate Meijin, Hon'inbo, and Juketsu titles. At 26 years of age, Kadowaki wishes to become active in Go again and pass the professional examination. Sai plays for Hikaru and trounces Kadowaki. After the short game with Hikaru, Kadowaki decides to train for a year before taking the professional examination. Kadowaki is surprised when Hikaru calls him "Pops" (Oji-san in the Japanese version) despite the fact that Kadowaki is in his twenties. Hikaru plays Kadowaki again in Volume 19.