I don't think one will work, unless you were joking. That just makes me think that the company things the audience is too stupid to recognize repackaging and might make think that a game wasn't good enough if they need to advertise that
It's also probable to beat dq in a day, provided the grinding of chars wasn't necessary. plus the demo covers the first 25% of the game, right? So maybe remind people that the demo exists, since I played that before getting the game and it made me want it.
coupons could trigger a person's impulse to buy because it's cheap for a limited time, but I don't think people who already own something get coupons for it. But it probably works better with a physical coupon than digital one
get some LPers to cover or speedrun it?
Though really word of mouth from popular and well liked internet sensations, or anyone with a large following on internet communities, recommending the game is probably the best option.
Also, please don't do nude choices for anyone, even if you're joking. not everyone will find that choice tasteful and may judge the game to be some stupid one-off nsfw fodder if they see that as a game tag, which steam is starting to get plenty of options for. But that might be my own bias right there.