This was described to me as a porn parody of Castle in the Sky, so I checked it out for laughs. It's definitely loose, but I can see the Ghibli inspiration at the edges, especially in the shapes of the hats that the workers wear and the characters' faces. Additionally, the voice actor who played the villain went on to play the Nine Tailed Fox in Naruto. As porn, this doesn't really work for me on a couple different levels. One thing is that the pace of Japanese porn is too slow and they payoff isn't necessarily as visceral because of their laws against depicting penisesand vaginas. Weird rule, but OK. It has resulted in a media culture that emphasizes almost completely different aspects of sexual experience than anywhere else. Now that I have lost your respect for knowing that little about Japanese porn, the more important part of why this doesn't work is a bit more personal. It doesn't align with what I tend to enjoy in this sort of story because the characters' emotions aren't at all relevant to the sex. There was no cycle of anticipation then release, and pretty much nobody was openly happy about it. They were only allowed to be happy about it if they were pathetically calling after someone who was in the middle of discarding them (so it's more pathetic) or they were a rapist. It is, proverbially, not my bag.

Oh, also, there was a story about a labor revolution and a big robot in there. Honestly, even though I didn't find the sex very interesting at all, that plot was even less interesting and barely mattered.

So, then, why a 4? Because it's surprisingly well animated and the scenes between the two main good characters were nice, as few as they were. They never had sex, which was a weird decision, but OK. There are some pretty landscape shots at the end, too. It was nice to look at when nobody was having sex, which is not really what you want from porn, but which is something I like to see in general, so sure.