She is 15 years old when the series begins, Nanoka is a bright and active girl, largely typical of her age group. She is attached to her newly-rediscovered older brother, and is easily annoyed with his brusqueness. Her friends periodically tease her about having a &quot;brother complex&quot;, which has more truth than she&#039;s willing to admit to anyone besides herself.     ~! Ironically, she comes to terms with her feelings for her brother before he does. !~

Saeki Koushirou works as a wedding planner, but his own love life is a shambles. His background makes it difficult for him to commit himself wholeheartedly to love. The child of a divorced couple, he lives with his father. He has a mother and a sister, but he has not seen them in years. After being dumped by his girlfriend, a chance encounter with a female high school student shakes Koushirou's calm and awakens new feelings in him - but he learns that the girl is in fact his sister, who will now be staying with his father and him. Yet, the feelings in Koushirou's heart... 
(Source: Anime News Network)

Born twelve years apart, siblings Koshiro and Nanoka were separated when their parents divorced and moved to different parts of Japan; as a result, they both grew up hardly aware of the other's existence. 
The story begins when 15-year-old Nanoka moves to Tokyo to live with her father and brother, the latter being 27 years old and employed by a marriage-arranging company. Koshiro first encounters Nanoka on the train one morning, and returns her dropped train pass. Despite their age difference, they feel a brief spark of connection before they go their separate ways. 
Soon after that, they encounter each other once again near an amusement park, where they go on an impromptu date. While riding the Ferris wheel, the two open their hearts to each other and discuss their recent romantic woes. Nanoka comforts Koshiro when he breaks down and cries, and he realizes that he is very attracted to her. Right after the date, they meet their father, and are startled to realize they are siblings. 
Koi Kaze is about Koshiro's love for Nanoka, his conflicting drive to obey societal norms, and Nanoka's growth into womanhood and her growing feelings for her brother. 
(Source: Wikipedia)

Nanoka Kohinata