Shinichiro Isumi, Hikaru no Go Wiki

Shinichirō Isumi (伊角慎一郎, Isumi Shin'ichirō) is a friend of Hikaru and one of the oldest Insei before he quit after failing the Pro Exam for the 4th Time. However he finally passed and become 1 Dan Player after training at the Chinese Go Assocition. Isumi is often considered too sweet and lacking in backbone, but he is generally polite and treats everyone with normal behavior and respect. There was only one instance where he talked back to someone, Ochi, who had berated him for losing three games

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Shinichiro Isumi, Hikaru no Go Wiki

Hikaru no Go #20 - Yashiro vs Hikaru (Issue)