Niwa ni wa Ninin is a collection of 7 short stories which some seem to be connected and some seem to be standalone. Maybe even the whole thing is one big story. You can try and theorize about it yourself if that interests you. But if not, that's ok too. I found this manga pretty calming with a mystic and mysterious atmosphere. In every chapter there's someone who knows something the reader doesn't thus creating a mistery to solve through the pages
I'm not a fan of complex stories cause I get lost pretty easily but I found Niwa ni wa Ninin entertaining and easy enough to follow to not get bored. So if you're like me and you don't like using your head too much, give it a try. But if you aren't and you like intertwined meaningful stories with metaphors and such, also give it a try, maybe you'll enjoy it even more than I did.
Overall I really liked it. If I had to describe it with two words I would say calming and mysterious, which is an odd pair but I think Niwa ni wa Ninin combines them in a beautiful way.