Oreimo, short for My Little Sister Can't Be This Cute, is a 12 episode anime based on the light novel series. It follows Kosaka Kyousuke, a normal 17 year old high school student. His life is pretty normal, with average grades and nothing of note. His sister, Kirino, is another story. She is a model, is pretty and has the perfect grades. Kirino outshines Kyousuke in every way, so much that his parents don't really care about Kyousuke.
Kyousuke and Kirino's relationship is not the best. Kirino openly scorns her brother (she has the elements of a tsundere) but this change when Kyousuke finds out that Kirino is secretly an otaku. Kirino is into anime and games but what makes it surprising is the genre that Kirino prefers. She is into eroge involving little sisters (although she is adamant that she does not have feelings for Kyousuke).
Kyousuke is forced into helping Kirino keep her hobbies a secret. Considering Kirino's image and the stigma against otakus, embarrassment is a natural reaction. While the first two episodes is somewhat average with some humor here and there, the third episode helps pick up the pace. Kirino struggles to find some sort of outlet for her addiction to anime, and all this culminates into a passionate speech by Kyousuke on why people should accept Kirino's secret hobby. It is hurtful when you see the two different sides of Kirino's friendship circle. Hanging out with one group hurts the other and you feel that Kirino is selfish for doing this.
It can be annoying and frustrating when you keep seeing Kyousuke performing some selfless act to help Kirino, yet she does not express much sincerity. While that is the tsundere aspect, it just feels Kirino is more hostile than sweet. What make sit worse is that in the later episodes, everyone knows the quality of Kirino's work is poor, yet she gets lucky and reaps in the rewards. Even after Kyousuke turns things around, Kirino never finds out and she has an annoying smug look on her face while she still has the attitude that she is the best.
Some of the funniest scenes involving Kyousuke taking on the blame or "admitting" that the troubling behavior is him all along instead of Kirino. It is when he says it that you realize that it does sound really weird or unusual as someone's hobby. In a bid to help Kirino sometimes, he has to ask his parents for help and spinning the scenario such that it involves him. Thus, he says stuff like his friends caught him carrying erotic manga and now wants advice on how to mend the friendship. Poor guy then gets all the glares and evil looks from other characters when he is actually the nicest person in the anime...
Some of the scenarios are melodramatic, and in that world, seems to demonize the hobby of games and manga. It puts a very negative connotation to the term otaku which justifies why Kirino was so worried about it getting out. One of the main themes involves trying to get everyone else to at least partially accept that that is a part of Kirino, a part that she will not give up on. Despite all the things that Kyousuke is forced to put up with, the one plus is his childhood friend Manami. Described as plain and average, when an episode comes along and focuses on their relationship, despite being a stereotypical scenario, it's still very sweet. They have the issue of developing romantic feelings for each other but is held back from knowing each other since they were kids. It's quite funny when Manami's family comes along and obviously tries to set them up.
The events from episode to episode can feel like it has time skipped a fair bit ahead. For example, the first scene of a new episode suddenly has a significant even happen to Kirino when the last episode only showed her starting it off. It can be jarring. The final episode has what you feel is a sudden shift in Kirino's attitude. It makes sense by the end though and is even a little bit sad. This is the point in the season where the feelings of both siblings are most apparent.
There are four additional net animation episodes. The first one is an alternate final episode. Most of it is the same as the 12th episode but the last five to eight minutes are different and is considered canon of which the next few episodes follow on. This is a weird decision but it allows the later episodes to focus on characters other than Kirino, and the tone is more lighthearted and with a lot of humor. It works really well and heavily contrasts against Kirino, portraying her as a lot more selfish and unwilling to express her emotions to other people.
Overall, the likelihood of you enjoying Oreimo is highly dependent on what you think of Kirino's personality. She is selfish, unreasonable and even on the rare chance she is grateful, she manages to still get under your skin. In other words, she's a typical tsundere but a bit more of the "dere" would have been better. The decision to cut off three episodes which has a significant amount of character development is an odd one and at the end of that, despite Kyousuke being popular with the other girls, you know that will always gravitate towards Kirino.
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