I lived in Tokyo for 11 years and Shimokitazawa, where Hiroko’s apartment (which is run and managed by an intermediary company) is located in my favourite area in the entire city. The location is stellar and within a 5-7 minute walk of dozens of bars, restaurants etc while still being totally silent and peaceful at night (just Japanese things). The apartment is basic with some eclectic furniture/design choices but modern, clean and quiet in a nice modern building.
One thing I would criticise and again, this is coming as someone who has lived in Japan for over a decade and who is familiar with both traditional futon and the much firmer mattresses here, is that the bed is EXTREMELY hard. It’s the hardest futon/mattress I’ve ever encountered. It seems to be a futon on top of a western wooden bed frame, which is an interesting combo (futons are usually laid on tatami mats which are much softer than wood). It made for a pretty uncomfortable few nights.