Review of Koi Kaze

Koi Kaze is the story of a girl and her brother 12 years her senior struggling with the fact that they are falling in love and can't stop it. It's a tragic story and a well told one. Art can be bad at times, sound is great, the main characters are complex and the background characters serve their purpose. Basic rundown. Not what I want to focus on. I want to focus on justifying the two things people will have major issues with going into this anime. The age difference may seem like an unnecessary part to add for most people. I mean there's already the issue of incest sowhy is this second layer of taboo important?

The fact that the male protagonist is 12 years older than the female protagonist shows that he is well aware of what is expected of him by society and throughout the series he struggles to fill that role and cope with his feelings actively pushing away the female protagonist most of the time. We can see that he's worn out and genuinely apathetic towards his life before she came along.
The female protagonist having just entered her freshman year in high school and just starting to have her period shows that she is hormonal, naive, and sentimental as a child should be. We can see her sentiment later when she make a brash suggestion when they're pondering their options of how to handle this relationship.

The dynamic these characters have would not be the same if they were much closer in age.

The characters being blood relatives and living together is the only reason most of the drama in the series can pan out to begin with. Had the female protagonist been just another random girl then the shared living arrangement and the entire set up for most of the drama in the series would have changed, fundamentally changing the story as a whole. Age would have been a much easier thing for the protagonists to get over with the obvious solution of "waiting it out" alone. The added conflict of them being related takes out any easy ways for these protagonists to deal with their situation.