Anime: Onii-chan Dakedo Ai sae Areba Kankei Nai yo ne!

What do you get when you put a brother, who secretly writes stories about forbidden incest, and his sister, who openly loves her older brother, in the same household without adults? OniAi takes an eyebrow-raising concept and mixes in your standard mindless comedic-based, slice-of-life harem. If you're looking for anything other than fan service and dirty talk, look elsewhere. If you're looking for the most unrealistic harem situation without resorting to magic/sci-fi, you'll find it here.

Animation:
OniAi matches up around average compared with comparable series. The show is drawn in a fairly bright and saturated palette that emphasizes the light-hearted mood of the series. Character styling is standard-fare harem. All the girls are pretty much as distinct as they come physically (different hair colors, different eye colors, different 3 sizes, etc.) as well as personality-wise. There's even a manager lady who vaguely reminds me of an older Misaka from Railgun.

This is a harem series, and an ecchi based one at that. My recommendation would be to watch the OP. If you like what you see there, then this may be a good match for you. There are a lot of nude scenes but surprisingly few accidental moments. Virtually all approaches are purposely made by the outrageously aggressive female cast.

Sound:
I don't particularly care for the light-rock OP with slightly flirtatious undertones and the cast-sung ED. BGM is likewise your standard fare accompaniment. Some of the characters have their own themes that becomes apparent after a few episodes but there isn't anything really outstanding about it.

The VA cast is quite varied. You have mega-veteran Eri Kitamura working alongside a really young Ibuki Kido voicing Aiiko. A lot of the "fan service" comes from fantasies of the girls so, like in Seitokai Yakuindomo, expect a lot of the ecchi to come through conversations.

Story:
OniAi is supposedly innovative in its premise. However, after what amounts to half an episode, it quickly diminishes to your standard harem-based confrontation. Yes, having a girl claim she's your blood-related sister and still wanting to sleep with you is a twist, but it can only get you so far. The majority of OniAi is composed of the gals fighting in pointless competitions; usually to win a favor with Akito that he hasn't even approved. There are some multi-episode parts in the latter half of the show, many of which are flashbacks explaining Akito's history with the girls. Ultimately, the plot really doesn't go anywhere so don't expect much from this department.

There is also hardly anything to hinge a "realistic" tag on for this series. Akito basically maintains what used to be an old dorm/apartment bound for demolition and holds a job as a writer so that he can live with his sister. However, it seems that other girls have decided to join in on the "action". Each of the girls is apparently from an extremely influential or affluent family and all of them happen to be on the student council. Oh yes, they also all happen to have an inexplicable crush on our standard, run of the mill protagonist.

Character:
The unrealistic nature of the members of the harem, combined with some pretty dirty minds for their age, make it relatively hard to relate with the cast. Yes, you do get a large selection ranging from your cute sister, a sadistic princess, a flat-chested childhood friend, a chuunibyou-suffering dominatrix, and a girl who really is way too young to even be included here. But there's nothing that really makes you think that they actually have a valid reason to like Akito. Some of these contenders have much more background explication than others but overall none of them really have any development through the story. As for relationships, our protagonist remains the nice satisfy everyone dude so don't expect any progress other than girls mysteriously popping up around him at "unexpected" times.

While there are some funny interactions and moments the overall character set is unconvincing and, as seen through character ratings, many of the girls aren't really what I'd call popular. I've seen some harems that go nowhere but in this case, you'll probably get more development if you watch something as plain as Minami Ke.

Value:
OniAi has its funny moments but overall comes across as a concept watered-down and mixed with other standard elements to make it "TV-appropriate". Ultimately, the final product isn't believable and doesn't go anywhere. Personally, I think I'm just tired of these "wishful-thinking" type harems where the dude is just handed everything. If you just want fan service and a girl constantly saying "oniiiiiii-chan!" then this might be good. Otherwise, I'd pass on this one.