Phi Brain: Puzzle of God - Season 2 Episode 10

Following the battle against Orpheus Order, Elena transfers into Root Academy and takes the Phi Brain kids and their friends on a vacation on her private island, where puzzling is forbidden. However, Kaito and the others have trouble relaxing due to the lack of puzzles. They soon get excited when they find a clue to what is supposedly a puzzle and go into a cave to search for it, not willing to listen to Elena's explanation. In the end, it is revealed to be the set of a monster movie the POG made which almost made them bankrupt and was kept a secret. Realising there's no stopping them, Elena turns the vacation into a Puzzle Camp, much to the annoyance of Nonoha.