One of the things that frequent viewers of anime will notice is that the brother complex is very common in anime compared to other media. There are a number of titles in which romantic feelings develop between a brother and sister that may or may not be blood related. More often than not, such relationships are with an older brother (or onii-chan) and a younger sister and are usually one way with the sister having feelings towards her brother, something that I like to call the Onii-chan Syndrome. There are varying degrees to which these relationships develop and so many anime have them that they seem to cover every situation.
The tamest example of Onii-chan Syndrome can be seen in Ore no Imouto ga Konnani Kawaii Wake ga Nai (My Little Sister Can’t Be This Cute). Kyousuke’s little sister, Kirino, is a closet otaku that enjoys visual novels with cute little sisters. While it is never explicitly stated that Kirino has any romantic feelings towards her brother, there are hints that she does have some feelings towards Kyousuke. Whether those feelings are romantic or familial is really up to the viewer’s interpretation.
The next level up can be seen in Suguha from Sword Art Online. Her feelings towards her brother are not immediately clear to any of the other characters, but it is made clear to the viewers. Despite realizing that she is in love with her brother though, Suguha does not attempt to pursue the matter any further due to the moral implications and the fact that her brother has someone else. While Suguha has Onii-chan Syndrome, she is able to control it while around others.
A more extreme example of Onii-chan Syndrome is Akiko from Onii-chan Dakedo Ai Sae Areba Kankeinai yo ne. Akiko openly expresses her love for her brother and proclaims to the other girls in the anime that he belongs to her. Much to her dismay, her brother does not feel the same way about her. Despite seeming like the ultimate case of Onii-chan Syndrome, there is some hint that Akiko isn’t really willing to go all the way with her brother. In one scene she was dared to give her panties to her brother, but simply couldn’t do it, bringing into question her devotion.
One little sister that does not have any problems giving herself to her brother is Sora from Yosuga no Sora. This is the most extreme case of Onii-chan Syndrome, not only is Sora madly in love with her brother, but they actually make out with each other and disregard the societal implications of their relationship. It’s questionable whether any of the previously mentioned sisters would actually go this far with their brothers, but Sora would definitely cross the line given the chance.
The Onii-chan Syndrome has become so prevalent in anime that it has been portrayed in every possible level, from nearly non-existent to a full-blown relationship. The series I mentioned above all aired within a couple years of each other, so it’s not hard to find dozens of examples of Onii-chan Syndrome. What do you think of the Onii-chan Syndrome in anime? Is it something you come to accept, like characters with blue hair, or is there simply too much of it?