This was one of the most comfortable places I stayed in Tokyo. The apartment feels incredibly homey and is well appointed, and the location was serene. The surrounding neighborhood is very residential, and the sounds of the park next door contribute to an almost "suburban" feel.
This doesn't mean the area is dead, however. There is an astonishing amount of good food in the area, including one of the 3 Michelin star Ramen restaurants in Tokyo (at least, according to my Googling), and Otsuka station makes it easy to get anywhere you want to go.
If you're looking for a peaceful stay in Tokyo this is the spot for you.
P.S. If you do stay here, check out Shilingol. It's a nearby Mongolian restaurant, and going there and chatting with the owner was one of the culinary highlights of my trip.