To beat yian garuga without even fighting him you have to get a spiderweb from the lady from the village or find it and when you start the quest go straight to area 7 where the old man is and trade him the spider 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 only have 1/3 of his life so he should be easy to kill ,if you choose to do this quest again after you killed yian garuga with only 1/3 of his life then you have to do the spider web trading thing again then repeat the trading spiderweb and so on.