An Akemi character animation illustration original drawing from the cult classic anime/hentai original video animation (OVA); Urotsukidoji, The Legend of the Overfiend. 

What's a douga ? Douga are production drawings that are used behind painted animation cels and used to make the cels.

What's a genga ? Genga (原画), Japanese animation terminology for key animation drawings, literally meaning "original pictures". Genga are drawings of important scenes made by senior animators. They are then used as model by other animators to draw douga. A genga is never used directly to make a cel and is usually not available for sale.

It's possible to find drafts of genga (rough sketch) but usually they are not available on the market. Genga and their drafts are much more valuable than douga.