Tower of the Sun

From Yen Press: One young man's boring college life changes forever when he shares a budding romance with a girl named Mizuo. And it all comes tumbling down when she, of all people, has the gall to dump him! Now with only his enormous (some might say delusional) imagination to his name, he starts tearing through the streets of Kyoto! A Japanese fantasy novel for every man who's been let down by love, and everyone planning on doing so.