It is a deconstruction of hentai that I found to be genuinely sad. The OVA is broken up into episodes while having the same main character but with a different background.
One of the best things about this anime is the way it takes the basic premise of any hentai "all women are there to have sex with" and deconstructing it to hell and back.
Scale of best to worst for each episode; 2, 4, 1, 5, and 3. Episode 2 was the best overall with episode 4 close behind. You could completely skip over episode 3.
Overall, Inma Youjo is one of the best examples
of plot-heavy hentai you are likely to find.