The smart thing in this game is to never run away from battles and get the exp. I learned this the hard way here becuase karin had no vp left and began each battle with no health. However I still beat this guy after a few tries. Use Karin to heal Atsuma and use Atsumas fire element attacks to do double damage. And also carry returns and curing powder. Also remember that Karin can take more hits since she is also water.