The author actually commented on it in the last volume of Hungry Marie (where the one-shot was included as a bonus).
"This is the one-shot that preceded the creation of Hungry Marie. Back then, I wanted to move away from Beelzebub for a more fantasy-oriented universe. I remember deliberately choosing a hero who resembled a pre-transformation Oga. Reviews on it were pretty good, so I tried to turn it into a series, but despite several attempts submitted to my editor I failed to make an interesting story out of it. In the end, for a change of mind I decided to submit him a storyboard of a story more similar to Beelzebub, and this time I remember getting the okay immediately! I probably won't get to use this idea anymore, so please read it to pay it a funeral hommage."