STORY:
There is very little to say here, the core premise of the story is the relationship between the main character and his sister (The Titular "Imouto"). Their gradual transition from pretty much hating each other to , still hating each other but in a cute way is the entirety of the story. The characters, setting and even the activities are just a vehicle for the Brother/Sister interactions.
That is all there is to the story, however this is not an anime that relies on story for engagement and I will elaborate in the next point.
CHARACTERS:
This is where both, the best part of the series and the worst part of the series comes into play. I am going to make a strange comparison but please bare with me I am going somewhere with this;
There is an anime called Mirai Nikki (Future Diary) and it is one of the most clichéd, stock-character, stock-plot, stock-action anime I have ever seen. It rips off from other media wholesale (Ex: A survival tournament held by an inscrutable entity, engaged by slightly superpowered characters face off to the death until there can be only one , in order to get a prize... sound familiar? it's highlander, though lots of media rips off highlander (COUGH Rozen Maiden COUGH)) and the action is very plodding, many of the action scenes are perfunctory at best (Ex: Wolf "fight" is a prime example of a lame action scene with almost zero suspense involved).
Almost all of the cast is completely forgettable given how terribly underdeveloped they are, they have poor interactions at the best of times and what little they have consistents of simple anime stereotypes (Hey, here's the jock character saying something Jock-esque, here's the Tsundere character saying something Tsundere ish, here is the older badass businessman pulling strings, etc.). The main character is unforgivably stupid and poorly written (Goes from a complete pansy to gunning down people in almost no time flat). But, the plot and almost all of the lacklusters characters were bolstered greatly by a single uniting thread; Gasai Yuno.
Gasai Yuno is the original 'Queen of Yandere' , her presence, her actions and her backstory (Mystery) form the only unique and engaging thread in the entire anime. She singlehandedly makes this anime go from pure trash to , pure trash thats entertaining. But is a single character enough to make it a good anime? in my opinion, no.
And this is where the parallel begins;
In Oreimo; The main character Kyousuke is actually pretty well written (For the most part), the supporting cast is extremely well written as well, with surprisingly complex motivations and development... especially for this genre, making them both deep and endearing (In my opinion). The setting is mundane but belies the reality of societal pressures and isolation of Japan, again, in my opinion it does this very well, showing the difficulty that the Japanese have when it comes to relating to each other.
If I had to grade only the main character and the supporting cast (Goth loli, crazy otaku girl, insecure model type, hilariously inappropriate grandparents, etc.) I would not hesitate to give this a 9 or maybe even a 10, but it has the REVERSE problem that Mirai Nikki had. One single character drags down the entire show... Kirino, the Imouto, is one of the worst characters, I have ever seen in any media. She absolutely anchors any scene she's in with her ultra tsun-tsun behavior and just completely intolerable, unjustified hostility.
Her character is nearly a black hole of entertainment. Where a little bit (Or even a lot) of tsun tsun (Cold, aggressive, hostile behavior) for a tsundere character is acceptable, this character goes so far beyond tsun tsun that she's just completely unreasonable and for me, draws away from the rest of the excellent cast. She is not tsundere, she's just a psychotic teenage girl with a major princess complex.
She becomes violent very quickly and unjustifiably so.
She treats her friends and family like trash
She acts very entitled to everyone's attention and even worship.
The worst part about this is, she gradually infects the other characters to tolerate and even worship her abuse. This is not endearing, this is not charming, this is disappointing because she actively sucks the "good" out of the rest of the cast.
But as I said, everything else, literally everything else worked wonderfully, in my opinion. One of my favorite episodes was an episode where the main character stays away from the Kirino Imouto and it was the best written, funniest and balanced episode, with touches of romance, slap-stick and situational comedy. It worked really well which is tremendously disappointing because it showed what could have been.
I know that I did not talk about the Art or the Sound, but that is because the female lead Kirino completely eclipses almost every other aspect of the show. Again, it is the reverse effect of Gasai Yuno; Gasai Yuno carried Mirai Nikki from bad to mediocre. Kousaka Kirino anchors Oreimo down from excellent to average at best. I can honestly say, I have never wanted to love an anime more than this one, but the cancer that is Kirino made it impossible for me to enjoy it on any level beyond "I can tolerate this".
I find very little to recommend here;
If you like romance, this is not for you.
If you like ecchi, this is not for you, despite the subject matter (You'll know what I mean) there is actually very little real ecchi here. There are doses here and there but few and far between.
If you like comedy... what can I tell you, I found the supporting cast funny but Kirino scenes overshadow the fantastic supporting cast.
That is all.
