Denjiro's appearance is unknown.
Denjiro once served under Kozuki Oden until Oden was executed 20 years ago. However, Kin'emon believes that Denjiro is still alive.
Along with Kawamatsu and Ashura Doji, Denjiro is considered by Kin'emon to have been one of Oden's most powerful followers, being worth 100 men in battle.
(Source: One Piece Wikia)