Good Harvest! Forest of Terror

S4 E6: Fumie hears about a camping site where people are going missing, and heads over with Shinnosuke and his dad to investigate. They follow voices coming from deep in the forest and discover a group of people who have been turned into mushrooms by the "Evil Mushroom King". The evil monster catches the Monster Busters by surprise, and they are all turned into mushrooms and truffles.