To beat yian garuga without even fighting him you have to get a spiderweb from the lady from the shop or find it and when you start the quest go to area 7 where the old man is and trade him the spide web for a special mushroom and wait in area 7 for the remainder of the quest and when the quest is done it should say you won the battle the next time you do this quest yian garuga will have onlt 1/3 of his life so he should be easy to kill and if you choose to do the quest again then repeat the trading spiderweb and so on.