Although released by Nikkatsu and marketed as Roman Porno, it is, in fact, a crime thriller with a light sexual undercurrent and an obligatory rape scene in a church. Originally titled Retreat Through The Wasteland, the distributor added 'Wet' to attract an entirely different market after director Yukihiro Sawada took the project in a direction not originally envisaged by the financier. It then became Retreat Through The Wet Wasteland.
The art below is from the reasonably rare Geneon DVD, but the art above, which is sensational, is the original theatrical art. I love the foreground angle and the intense background biker action. I find this super-erotic and ultra-evocative. It constantly refreshes my love of cinema.
The film is a flawed but compelling gem.