It is apparently an original doujinshi, called "Bloodless Blues," by Sin Takekawa. It features a world where vampires and strange semi-disembodied spirit girls prey on innocent maidens, and a battle couple who look oddly like angelic Gwendolyn and long-haired Oswald fight these demons. Here's the catch: it was published fifteen months before Odin Sphere was released in Japan. The couple acts like Gwendolyn and Oswald--fighting together, obsessively saving each other--but their names are Rosalyn (ロザライン) and Orlando (オーランド).
All in all, it makes me wonder if this Sin Takekawa is an alias for someone in Vanillaware involved in the creation of Odin Sphere, but there doesn't seem to be a lot of information available to confirm or deny this, even if I could read Japanese.
Question: the doujinshi is 24 pages. Do I scan it?