D.C.: Da Capo (2003)

Somewhere in front of Japan’s coast, on the small crescent-shaped island Hatsunejima, the magical cherry blossoms bloom throughout the whole year. While Jun’ichi Asakura, attendant of the last year at Kazami Junior High School and descendant of a witch, is spending his days together with his beloved adoptive sister Nemu, a mysterious girl is repeatedly appearing in his dreams. But from the moment when this mysterious girl is identified as his cousin Sakura Yoshino, who left six years ago for a stay abroad, their days in peace are counted. A time full of conflicting emotions and old returning promises for Jun’ichi begins.

Source: www.anisearch.com/anime/3482