I have only read the book, but is it possible it's from the anime? There already seems to be a comment asking what song it is, you could always wait. ( Or was that you that made the comment).
Best of luck finding out what it is, sorry I wasn't much help, but thanks for linking the song. ( I ended up putting it in my phone since I liked it so much).
________________ Yes yes I know I make longwinded comments, but that's just me >.< I should proof read my comments more, but I won't ... I really should though >.> So keep in mind I'm filled with typos
Reading FAQ and Forum Rules is very helpful ... so go read them if you haven't yet. Ex. -You could find out how to link mangas. Along with other useful things.