When I signed up to spend the six-or-so hours of my life at the start of the season watching this show, I knew Oniai was not going to be the next biggest thing in anime. It's not going to sell a billion copies of Blu-ray and DVDs to otaku worldwide, nor will it win any awards. I was not sure if I can make it to the end. I was not even sure if it would make me laugh, and I'm an easy one to please.
At the end, I can confirm with you that, yes, Oniai, short for Oniichan dakedo Ai sae Areba Kankeinai yo ne, is not the next Evangelion. It's not even the next OreImo. I would even say it's what you would expect of it, going in. It's however, an anime that actually has a profound story to tell, and that alone warrants at least a close look at the end of my journey here. Click on!
In a lot of ways the final broadcast episode does a great up summing up the theme of Oniai. Sure, in a nutshell, this is a harem anime about a high school boy and his charges. Even more so, the theme is centered on the way how the different girls in Akito's life changes him for the better, through better or worse days in their lives. Akito and his friends face various challenges, and in this particular anime, Akito, the girls and the viewers share a laugh at the end of the day.
The final episode, as per Oniai's usual style, has a massive lead-in (over 13 minutes!) to the opening credits. It details the start of Anastasia's relationship with Akito, and more importantly, how she shares the same exact bond as Akito, in how she both loves the way she feels about Akito and how Akito's harem means to her. Perhaps a layer thicker than the average harem, this has been a persistent theme within Oniai: Not only is Akito the nexus of the story's relationships, each of the girls have a thing for at least one or more of the other girls--may they be true rivals, substitute stuffed animals, or an equal-opportunity carnivore's meal.
In between the A and B parts of episode 12 stands the main gag--the ghosts the girls spotted in episode 11 were real, and at the end all the girls (including Akito's editor) spent the night in his room, with the final punchline revolving around Anastasia going commando. To that end, humor has always been the one major failure of Oniai. I'm not sure if it really is trying, but I suppose there is a token amount of it to break things up.
Much more engaging, I thought, was the final segment in the episode--a heartfelt dialogue between Akito and Akiko. It spells out very clearly what the show is really about: it's about love. It is fitting that would be the case as this sibling pair test the limits of their relationship--to what degree can it be healthy at all? And what is Akito's true position in regards to Akiko? I thought the conversation really made that idea profound. If we were to abandon the shallow notions of biological sex being the one expression of love, and acknowledge that things between siblings can be a lot more complex even at Akiko's level, Akito's grand plan begins to make sense. Oh, don't mind the major spoiler on your way out of the door.
And isn't Oniai all about that? Once the story goes past the initial gag about boning one's younger sister, it becomes a straightforward friends-gets-to-know-friends story with a lot of inappropriate gags and cold intros thrown in. Akito holds back because he loves Akiko, and Akiko simply expresses her affection in different ways. In fact, Akito acts out of love for everyone else, and everyone does more or less the same for him. It might mean to leave him alone; it might be sharing the burden of housework; it might even be taking up a persona different than the one you normally do. It begs us to think about what loving someone really means--is it really so simple?
In the end, however, Oniai is nothing so grand. In fact I think it's a miracle that this fundamental point got across as well as it did, underneath all that late-night anime trapping that some might call the cancer of the industry. I think it's not nearly so bad, but what might work for a light novel might be much more difficult to get across visually. If the fanservice, the weird antics, the interesting character designs, the unique voice acting or the strange way the show is directed doesn't do anything for you, I can't imagine why you would put yourself through Oniai. The challenge, though, is the opposite--if you want to just turn your brains off and enjoy this show, you are really not getting your time and money's worth. All of that puts Oniai between a rock and a hard place.