First he will make a copy of himself and all you need to do is just
attack (square) and block his attacks (R1). He will make a copy of
himself three times. Then after you beat the third one, run to the real
guy and you will do an upward swing. He'll fly out the window but he
won't give up. You two will talk for a minute then you will fight him
directly. But all you need to do is just five easy swings and he's dead
and game over.