Isumi is a young man calm and reflected. He doesn't hesitate to cool down Waya and Shindo feelings. Moreover his go show his personality. He always takes the time for the reflection and sometimes he puts some challenger who loves play fast (Fuku, Le Ping and Shindo).
He is always gentle and nice, he never answers to Machiba's provocations and sometimes he is a little naïf.
But, under his sweet manners, Isumi isn't without personality. So he doesn't hesitate to frown at Mashiba when he provoke him excessively and he also said to Ochi to shut up, can't endure him.

At the end of the test he even feels a little jealousy, when Waya succeeded the Professional level. Then he hopes that Hikaru will lose for have a chance to participate to the play-off. Unfortunately it will not be the case, disappointed, he go away in the rain, dropping the go for a moment.
Nevertheless he stays honest and loyal, even if he is tented to cheat against Hikaru, that will be make him question.
He also can show him happier, like when he compares the similarity between Waya and Le Ping.

Isumi is very gifted to play go. He makes go of the famous 'Kyuseikai' club and many persons hope that he will become a professional quickly. It's the case of the insei, of some professionals and of the reporter Amano-san who seem to know him well. He even impresses Kuwabara-sensei during the Shin shodan series where he win against the old man by 6.5 points. His master trust in him and send him in China for, at the beginning, play some game wit Chinese professionals.
Unfortunately, in spite of his talent, Isumi haves faintness. He misses trust in his go and he internalizes his feels so, he checks him and he lose.

Since the pressure is too strong, Isumi cannot manage it. So he loses his match against Shindo because of an error and a cheating, before slump during some games. However he will succeed to surpass his disability during his travel in China thanks to Le Ping but especially Yang Hai.
Controlling his faintness, Isumi become a professional undefeated.