Aki lives a charmed life. Popular, beautiful, athletic, and at the top of her class, she rules the school, and at home, her younger brother Sora caters to her every whim. Her younger sister Nami, however doesn't have it so easy. The small-chested and sarcastic girl is in love with her best friend - who has a crush on Nami's twin brother Sora - but her life could be worse: she could be her brother. Slight, feminine, and bullied by his twin, Sora cooks and cleans for the entire family. In addition, he harbors a deep-seated lust for his older sister, Aki. Will Sora get over his fantasies or give in to his desires? Will Nami ever win the heart of her best friend? And what does Aki want out of all of this?
If relationships between a brother and a sister are what you are looking for Koi Kaze and Aki Sora are the series for you. The character development in either one is not lacking. These two series also demonstrate the gravity of a relationship in this type of world.
Even though Koi Kaze has a more direct incest relationship between brother and sister, the dynamic is faced in Da Capo as well, though not to such an extreme. There are excitingly dramatic moments in both series as well as an overwhelming seriousness for the characters and the trials they face.