What would happen if you'd be forced by a mysterious force -be it good or evil- to be extremely honest ALL the time? What would happen is, at first, that you could not have any kind of typical healthy relationship with friends, family or society. The full weave of social interactions would be destroyed by the total disrespect to societal norms, appearances, empathy or egotistic desire. You'd be a monster, or simply put, someone really awful to be near of. It would be awful because from such a stark tongue there would get out anything else but the truth. The hard truth, the things youdeny in front of the mirror everyday, those issues you expect to solve themselves, the problems with your neighbors that you don't want to have a fight for. But that's just by yourself, in other people's eyes you'd be that nasty m*therf*cker that goes around the world pointing out ugly noses, pleasant lies and reading people's t-shirts loudly and by doing so denouncing the stupidity of it all, the eternal doom of the suburban existence, the emptiness of our hearts.
I may have described a monster but that's precisely what this anime is about: monsters. In the very first episode we see a home spirit moving to Tokyo in hopes of have a good life. But what a surprise she had when in the city she finds that the man has degenerated into a slug that crawls between the train and their home while constantly lying to themselves to feel fine. Tatami-chan, the monster, clashes every time she tries to live the tokyoite way: in the train, dating, in the park and in this resulting clash one can find amusement that in the apparently nonsensical jokes, a cold, hard truth hides behind.
The way of life of the contemporary (Japanese) human is thoroughly analyzed and criticized by the author by the magnificent vehicle of a non-human observer, unmasking aspects of our conscience that we maybe couldn't have put into words before. A example of this genius reaches its top in episode 5 where the social networks are the topic. An anime like this is certainly a gem in the mud that dared to do what few dare. The seemingly poor art and almost non-existent animation take a secondary place after you begin to catch the undertones of the anime.
Apart from that, the character design is cute and the music is really enjoyable, specially the ED song -which I've been searching like a madman- by Oresama. One of the biggest flaws tho, is that it's too short and the episodes, too few.
I think I've said enough but I don't want to end without commending you, anime fan, to take a hard and extensive look of yourself in the mirror and try to find the reason behind your acts and your place in this life. It's hard but maybe not much after watching Zashiki Warashi no Tatami-chan.
Sorry if it's not well redacted, I'm not a native English speaker.