I just had a wonderful 8-day journey in Mari's. The things below might be your reference.
First you should know that you are going to live with a mom and a son.
And you are going to share most things with them. Of course it will not be as free as in hotel, but it's more alive than living alone. Mari is nice and helped me a lot when I'm in trouble.She cooked me delicious breakfast for 8 days(never the same).
The house is quite and cute. There's a park about 2' from the house which is a good place to have a walk or do some running.
But the house is a little bit far from the subway.(about 17' on foot) And the room is small. If you don't care these, considered the prize, it's really good place to stay in Tokyo.