Jun'ichi is the main protagonist of the series. He is a second year high school student and had a quarrel with a transfer student, Yuuhi Katagiri on the first day of school. It turns out that Yuuhi is his fiancée as arranged by his family. He had a reputation of a delinquent in junior high school until his sister Minato decided to move in with him. He has a snarky attitude and is often teased by everyone around him, including his teacher. His life takes a drastic turn with Yuuhi entering his life. When he first met her he had the impression she was a helpless girl and kissed her because of a misunderstanding. After that, Yuuhi becomes much more violent towards Jun'ichi. Since Yuuhi is often harassed, he finds himself protecting her; as time progresses, their love for each other grows, even though neither of them will admit it. Throughout the anime series it is hinted that Jun'ichi has romantic feelings for his sister Minato, but he is reluctant to admit this even though he sometimes has fantasies about her. In the final episode, he realizes that he cannot live without Minato and confesses to her. In the manga however, he and Yuuhi end up together, as he also has feelings for her.

(Source: Wikipedia)