Upon entering Tsuta Ruins, ignore Issun's suggestion of trying to use Water Lily in the poisonous water, as the poison will immediately dissolve the lilies. Head left, Power Slashing plants on the way for food (or Yen, if Amaterasu already has a full Astral Pouch), examining the Blockhead's back at the end. Don't forget to bloom the Giant Bud on the small island near the Blockhead. Then head right, chopping the vegetation on the way, remembering to bloom the Giant Bud (contains a Traveler's Charm) and the treasure chest in front of the door to the next room (contains a Vase). In the next room, simply apply the normal tactics for Cursed Trees to purify the ones here. Note that on the small island in the waters, there is a Clover. The door to the next room is on the other side of the walkway