Brave Story: Shinsetsu

Wataru Mitani's life was as ordinary as any other until he found the new transfer student to his school battling a giant monster in his neighborhood. In search of clues to this, he finds a door to a world called Vision, a fantasy world where magic exists. When Wataru’s life starts to crumble around him, he embarks on a journey beyond the door to change the fate that has befallen his family.
(Source: Tokyopop)