Okay, so Ken has only appeared in one drama, and it was an obscure, short one at that. He starred with Kanno Miho in the 1998 tv asahi production Setsunai ~TOKYO HEART BREAK~
. Considering it was created in 1998 before Ken gained fame in the industry, he most likely starred to promote his music. He does, in fact, spend a good portion of the drama singing on the streets.