Asura Cryin' Season 1 Episode 14 The Disappearing World and the Ruins of Memory

"Tomo's misunderstanding gets the Science Club in trouble once again, and as punishment, the members are made to clean the school pool. However, Tomoharu and the others follow a suspicious koala and find themselves in a labyrinthine underground tunnel system. Led by the koala, Tomoharu and the others find themselves at the Rakuroa ruins...!"