Uncle of Junpei and Kanta, as well as the brother of Tatsuo. Throughout the movie, he is a very carefree and rather childish guy whom "doesn't know how to die". In the beginning, he was secretly travelling off the island with the help of Junpei's bond fire. After having a fight with his brother, Tatsuo, over the boy's teacher, Sawako, he went out and got caught taking the supplies cave Tatsuo had in secret. It is thought that he was the one who ratted out Tatsuo to the Russians, but he denies it. Once landed in Russia along with Junpei, Kanta, and Sawako, he seems to grow up little by little, trying his best to continuously keep the group out of harms way.

(Source: Wikipedia)