Only that from what I can tell in the anko the previous inhabitant is still alive, in a way: The "special moss", which what the anko is about, not only provides the munch-munch for the yukkuri, but it reaches a certain point the moss will start growing on the current inhabitant, converting it into "soil" and preparing the yukkuri terrarium for the next yukkuri.
ParticleMan said: The anon younger sister seems nice... but probably doesn't even consider Reimu a pet, only a toy. This isn't going to end well.
Too early to judge just yet. The older sister looks at the yukkuri as nothing more than accessories (note the strap/keychain attachment), but the younger sister might treat little reimyu differently.