Ooh I get it!
At first I was confused about this sequel because it was so different to "Whisper Of The Heart" but now I think I understand it.
I think this may be a story written by Shizuku.
After all The Baron didn't live in his own little house in "Whisper Of The Heart".
People believe that it is called "The Cat Returns" to announce the return of Baron, however I think it would make more sense if the cat that "returns" is Yuki seeing as Haru didn't know Baron in the first place so he wouldn't me returning would he? He'd be completely new! :}
One thing is though; why did they settle on Muta and not Moon? It is the same cat isn't it? o.o