Ni No Kuni: The Successor Of Light And The Cat Prince summary:

High school student and kendo club member Tasaku Arizawa lost his parents and lived alone with his younger brother Tsubasa. Then one day, Tasaku was attacked by a man in black and ended up being pulled into the alternate world "Ni no kuni" through a "gate" that suddenly appeared. This was a world of magic parallel to the real one he came from. Through the use of his suddenly awakened "un-magic", he was chosen to be the saviour of the world by the former prince of the Goroneir Kingdom, Rosso. In order to reunite with his precious younger brother, he vows to slay the Demon Lord Sham.