Tenshi Kinryouku, Koi Kaze Recommendations
I recommend Angel Sanctuary and Koi Kaze because they both center around unlikely love interests. Both animes feature a serious look at incestual relationships between a brother and sister and how they deal with their feelings, society, and the repercussions of such a relationship. If you're looking for an atypical love overcoming all odds type of story, these two animes are a good place to start. Besides the taboo love themes though, the main difference between the two is that Angel Sanctuary is heavily fantasy based, while Koi Kaze is a set as a reality drama.