If you appreciate modern Japanese architecture, you can't miss staying at Kana's house. The polished concrete harmonizes with vertical panels of wood and is very satiating to the eyes - and that's just the aesthetics of it.
On hospitality: Kana goes up and beyond in hospitality. She is responsive from booking to check-in (no matter how far out you book - we booked months in advance). Even while staying in her home, Kana made a point to check on us everyday to see how we were doing and even made recommendations of places to visit.
On amenities: Everything you might need as a traveler is provided -- from q-tips, cotton pads, toothbrushes, lots of hangers, slippers, a long mirror, and even travel brochures -- Kana had the forethought to provided these for her guests. We had a very lively toddler with us who enjoyed the place just as much as we did.
On the neighborhood: Koenjiminami was great for us because we wanted to be close to Tokyo without being in it. Just down the street from the apartment are restaurants, boutiques, cafes, convenience stores, and even a pet shop if you fancy marveling at puppies and kittens. There is a huge array of places to check out, there is always something fun and interesting to see just 5-10 minutes away. I want to highlight the boutiques, the nearby boulangerie, Jonathon's (where we ate breakfast everyday), and even the Yamato takkyubin drop off center is not far. It is also worth mentioning that the neighborhood is very safe considering we never locked our front door every time we left (sometimes for hours at a time) -- all of our stuff remained exactly the way we left it!
I highly recommend this place for any traveler looking to immerse themselves in the feel of day-to-day life in Tokyo.