Katchan is the sempai to the man characters. Ichimatsu thinks of him as a big brother. Ichimatsu called him a womanizing gorilla.
He has a little sister who looks like a man.
He has been shown to be very popular among the women at school at times.
In middle school he was always challenged by and defeated ichimatsu. He sometimes gives profound words of wisdom.
Katchan is attacked by juuzou on the roof and nearly killed. After he recovered he was told the truth about ichimatsu, takezou and koume. As well as the truth about juuzou and the rest of the people involving the incident and everything that happened and well as to what they have planned on doing from this point on.
It seemed at first that he didn't believe them. However he did, because he know neither ichimatsu, koume, or takezou would lie to him. He did questioned why did they have to fight, and would this mean that he would never see them again. They assured him that they weren't going anywhere. And the must fight to protect the innocent people.