Once you get past that whole strategy part in the game you will get up to the boss of the game. Arrows are useless against the boss. The boss will rush at you when he does you have to slash him. When you do this he will most likely jump and throw spears when he is in the air you have to try to slash him when you do don't slash across slash down so it doesn't miss. You will have to do this several times to beat the boss.
The strategy part really doesn't require any strategy i just went straight for the boss's tent. but yeah just use a short stroke to make him jump then a vertical slash while hes flying bottom to top works best.