Kumagawa Misogi, more known as Kumagawa, was a nihilist who believes that there is no point to life or reason to be born. He has absorbed all the negative aspects of the people he met, failing at everything and losing to everyone at everything. Medaka attempted to reform him, like she had done to her other classmates, but Misogi proved to be beyond her influence. Medaka describes him as a compulsive liar who places no meaning in trust or doubt. As a negative person by nature who could kill a person just as easily as he could breathe, Kumagawa thinks nothing of the lives of the people around him and could take them away easily. Despite the immensely negative personality he possesses, he has a purely positive look regarding himself and has always been seen smiling. As a child, he was tested for abnormalities, but was believed to be normal.

He is the King of Sindria and the leader of the Alliance of the Seven Seas. He was 14 years old when he first captured a dungeon, the first dungeon ‘Bael’. Since then, he had sailed the seven seas and captured seven dungeons. He is known as the ‘Legendary Dungeon Capturer’ being the master of seven djinn. He is also commonly known as ‘High King of Seven Seas’. His nickname is Sin. His name is based from the ‘Sinbad the Sailor’.