Base Black

An ero-terrorist who appears in the anime's last episode. He personally knew and worked alongside Zenjuro and planned to unlock a secret vault filled with erotic treasures using an artefact that was passed down to Tanukichi. He gathered the main cast to a resort via false invitations and challenged them to a duel for the artefact through Yakyuken. He noted on his satisfaction on how Tanukichi had grown up like his father before him when he departed.

(Source: Wikipedia)