I imagine it's the same as the dev, karaage catapult, which is listed in the upload info. If the art was done by someone else they weren't clearly credited on the DLsite page, at least as far as I could see
Could've been me, I will loudly complain about that being shit design at any given opportunity. I'll still play some with the more interesting art (such as this one, huge succubadonkas) or mechanics, but I'll bitch and moan about it. It's also one of the reasons for my current game playing as it does