These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Koi Kaze
Audience-Alienating Premise: Koi Kaze is a shining example of this. It's squick enough because Nanoka is sixteen and her love interest is in his late twenties. It gets unbearable when you learn they're brother and sister. Even the most avid Brother-Sister Incest fans stay away from the series as it's too realistic for them.
Its also a very touching story, with one of the more believable and heartfelt romances in anime. This anime isn't cheap pandering of fanservice, nor does it ignore the realities of what this kind of relationship entails. You don't have to be an incest fan of any sort to enjoy it, just open-minded to accept the premise, so the above sentiment is understandable but definately not shared by everyone.