Kaien Ōsugi is a Kickboxer who compete's in the DofD tournament. He is a member of the team Hayato Fūrinji battles while the latter disguises himself as Garyū X. Kaien is easily defeated by Hayato's kicks which prevent him from standing back up and continuing to fight, all the while making it appear as though Hayato was not moving at all.

It could be deduced from his team that he teamed up with or studied under Gorobee Rofusagi at some point prior to the DofD.