Lunatan: 1 Man Nen no Himitsu  

ルナたん~1万年のひみつ~, Luna-tan: 1-mannen no Himitsu, ルナたん～1万年のひみつ～, Lunatan: 10,000-nen no Himitsu, ルナたん～巨人ルナと地底探検～

In a world that thrived due to the energy of titans known as luna, there existed a land. this land was crucial for maintaining global prosperity. however, a catastrophic tsunami struck the world, leading to the destruction of this vital land. the story takes place ten millennia after this devastating event, deep underground. mokugyo and toriiruka are the main characters, who are unique animals. they ponder, "why are we here?" and express their belief that they were once in a tranquil location. could you clarify what transpired ten thousand years ago? additionally, is it safe for mokugyo and toriiruka to return to the surface?