What if, these yukkuri solved the box, thus allowing demonic creatures to pass into their dimension. Those hellish creatures being called humans, who would take over the yukkuri's world and forever seek to torment, enslave, and/or annihilate the yukkuri race. Maybe that's how it all started, I always just assumed humans came first, but perhaps its all the manjūs' fault after all. My mind has been blown. (Also, all my information about the cube just came from literally 15 seconds of Wikipedia so I take no credit for being a part of a fanbase of what seems could be an excellent fictional universe)
lol, some people have trouble with the concept of conservation of mass, I guess. It's already impressive enough that they can stretch the laws of physics in turning anything into beanpaste.