I'll keep this short like the OVA, but first let me say: this was terrible, actually terrible. I'm usually completely against people giving an 1/10 if they've watched a full episode of an anime as it's therefore no longer 'unwatchable', but this was as near as it gets. My first ever 1/10 and I'll explain why:
So why the 1/10? Well in all honesty there was no real story, no plot as such, just Imari getting dragged into a room and being raped, she actually seems to enjoy it by the end but that's literally it, no joke. If that can be called a story then that was it, it was stupidly simple, predictable and may well leave you with a 'what in the world have I just watched!?' type expression on your face, I know it did me.
Ok, yeah so give the anime it's due, despite being terrible in most areas art wasn't one of them, it was drawn well and animated above average, no real complaints here although it really always is a matter of personal taste with art style, this one's up to the individual to decide.
No real problems with the sound either, everything was clear and I guess the sounds used were appropriate for the situation and fitted the mood of the anime, but looking at things on a larger scale it wasn't anything outstanding sound wise, while the sounds did fit the mood it was your basic oohs and aahs you'll find in hentai, nothing out of the ordinary.
Now while the characters played their roles decently they were both stereotypes and done nothing to break those stereotypes: the rapist had the evil, generally quite intimidating and menacing tone about him, looking only to get what he wants and Imari playing the seemingly innocent victim. In the 7 minutes we're given there really is no time for character development or anything of the sort, even if you've seen the Bible Black main series there's nothing that will make Imari or the rapist any better of a character in this OVA for you. The characters are quite plain despite playing their roles decently, maybe I'm being overly critical of this considering it's only a hentai OVA, but I'm only providing a guide for others here and am merely sharing my thoughts.
None, I can honestly say I didn't enjoy this one bit. I hate the idea of rape and did not enjoy watching it. If the anime's purpose was to arouse it failed, and failed quite miserably at that, I also thought the anime was executed quite poorly and done with quite strict character stereotypes in mind.
On a final note: unless you're a fan of hentai and rape in particular you should avoid this, it really isn't something I'd recommend to anyone, even those who consider themselves hentai fans. There are plenty of better ways to spend 7 or 8 minutes of your life.