Yori Yuuki

15 years old, and Iku's twin brother. He is intelligent and somewhat cold, but has a hidden soft side, especially for Iku. He has been in love with Iku since childhood and embarks on a relationship with her, even though he is tormented over their incest taboo. Halfway through the series, it turns out that Yori is Iku's half-twin brother and he was fathered by their father's best friend, who slept with his mother in the day of her wedding. When their parents find out about their relationship, they run away and act as a normal couple until they pray at a church. Afterwards, he tries to end the relationship by leaving Iku without telling her, hoping time and space apart will cause their feelings to fade. 10 years later, he and Iku reunite and Yori states that he is still in love with Iku.

(Source: Wikipedia)