The song is "Terzo Quadro (L'incontro)" by Latte E Miele. The anime is My Beautiful Girl, Mari.

My Beautiful Girl, Mari, also known as My Beautiful Girl Mari, is a critically successful South Korean animated film. It follows the story of a young boy during summer vacation and ascends into flights of surrealistic fantasy, which may or may not be dream sequences.

http://en.wikipedia.org/wiki/My_Beautiful_Girl,_Mari