Kenta Uchino (Teppei Kuze in Mebius) plays a karate guy named Masaru Honjou (I think that's how to write his name). Not much comment except that the viewers didn't get to hear his real voice in this episode (the voice Honjou spoke with belonged to Kintaros, the Imajin who possessed him). According to the preview for Episode 10, Kintaros will eventually leave Honjou and possess Ryotaro, so I'm guessing that Uchino's character will only last for one more episode.
Generally speaking, I found this episode to be a bit of a yawn, and don't think I would have posted anything about it if not for Uchino's appearance. Nevertheless, I intend to keep watching Den-O for now, since it does have some enjoyable moments (Momotaros & Urataros are so hilarious together, Ryotaro's actor is great in his multiple personalities, Ryo's bad lucks are unbelievable, but oh so very funny, and Climax Jump rocks so hard).