We enjoyed our stay at the apartment, the area is very nice and close to public transport, just around the corner from the Yamanote line stop Otsuka. The Yamanote line is a JR ring line, it is easy to get to nearly everywhere in the city center using the JR pass, if you don't mind walking a bit, you can avoid using Tokyo Metro lines all together.
There is a nice tram leaving from Otsuka station, too (but which cannot be used with the JR pass). At the station there is a map with all sights (parks, shopping streets and temples ) around the stops of this tram line.
The apartment is big enough for a family of four, but walls in between the little rooms are thin.
The kitchen is equipped for breakfast, there is a fridge and cooker, too. It was nice to have a washing machine for doing a little laundry during our stay.
There are many options for eating out near the house, for Ramen noodles, seafood BBQ, Burgers, Pizza and so on.
We liked in particular the comfy bed and the playground nearby.