WARNING : 13 year-old reviewing hentai below. He must be a badman.
[SPOILERS/SUMMARY IN THIS PARAGRAPH]
So basically, Airi the tsundere bitch gets stuck in a cave with her rapish step-dad and they proceed to fuck to "conserve body heat". Shortly after, they meet a childhood friend which has some sort of magical talent for turning into an identical copy of someone. Then they fuck with two Airis and it all turns out to be a dream but it isn't actually.
[A BIT OF SPOILER]
Thus, it gets a nine from me. Hentai is supposed to make you go "oh yeah, this shit turns me on", not "they forgot
to fill a plot-hole!" (they have other holes to fill), or "but those breasts aren't natural size!". And that's where Oni Chichi : Vacation succeeds for me. In the scene in which they are taking shelter, I really liked Airi's clothes, and the animation in which she was promptly fucked. The sounds are really well done too, they sound just like an Asian girl being deeply penetrated by a 10" cock (I know this from personal experience). I particularly enjoyed Airi's high-pitched noises as her dad was twisting her nipples. +1 brownie point for the somewhat-obvious hentai lines which turn you on 90°. You know, "You're going to put your trashy dick in my wet pussy?", "No, don't fuck my virgin cunt" and the like. Good stuff.
[CONSIDERABLE AMOUNT OF SPOILER]
In the next section, Kou-"chan" and Airi-chan encounter Mari, an osananajimi (hey look at me I know some random Japanese, therefore I am Japanese) of Kou's. He proceeds to tell Airi how he liked her and how they used to have fun. And then she FUCKING MAGICALLY I SWEAR changes into a virtually identical copy of Airi, except not in seifuku (+1 brownie point), but in revealing Christmas cosplay (+1 brownie point). Do I even have to explain what happens next?
Well, they sit down for dinner, enjoy a nice, home-made casserole and then discuss the political state of Lithuania, of course. As in, self-cest of some unidentifiable kind occurs and Airi watches "herself" fuck her step-dad only to join in like a sane normal person (+2 points for not only self-cest, but threesome-ious self-cest). -1 point for boobs that look like they've been drawn by a 3rd grader on the wall under a staircase with wax crayons. For fuck's sake, even Hotaru Shidare from Dagashi Kashi doesn't have melons that big. However, +1 point for the deeply philosophical conversation that Airi and Mari have whilst riding Kou's face and dick, respectively. Then they pass out on the floor.
[OH COME ON, THIS IS A HENTAI. DO YOU REALLY CARE ABOUT SPOILERS?]
Airi and Kou wake up in a hospital to be greeted by a worried Marina (his other underage daughter. My my, that works out well) , and informs them that they've only been found due to a loud raccoon making noise. Thank god that a raccoon scraping against a tree is louder than a hairy old man raping his underage loli daughter in a cave. Then, Kou tells Marina a little bit about Mari-nee (see a similarity between "Marina" and "Mari-nee"??) and she instantly dismisses him as a pervert. Airi then remembers Mari and asks him some questions that made him realise it wasn't really a dream. Although it could've been. Kind of.
The video then ends with a still shot of Airi smiling and happily exclaiming that her step-father is a pervert, as you do. I believe that Oni Chichi in general explores the thought-provoking ideas of the Lolita complex, Stockholm syndrome, The Weeb Effect, and plain ignorance for the sake of being fucked in the vaginal area.
Overall, 9/10 anime would watch again. Don't see why people think this is "fucked up" when they've never seen Boku no Pico or Kodomo no Jikan (one of my favourites in terms of hentai).
Rated - "R" for "Raping your underage daughter with a copy of herself in a cave is completely fine if you tell her it's for survival".
Hey, I'm Vice and I'm doing this so YOU can pick the right fapper for tonight.
Hentai Subgenre: Sequel.
In Short: Airi and her step-father have lots more sex, initially against her will, until a new pussy joins the party. The new girl is an old friend of the step-father and is also a dress up genius enabling herself to look exactly like Airi, making the sex all the better.
Best Scene: after a little skiing accident when Airi and Papa are in a cold cave, pop decides to rape Airi unzipping here snowsuit and plowing his shivering daughter in the snow.