Great value. Hard to find a place this clean/new at this price. Definitely a minimalist experience. There is only about 1 square meter of standing space in the apartment (apart from the entrance / foyer), so I wouldn't have wanted to share this space with another person as it was already tight enough for me as a 6 ft (183cm) male. I had just enough space to do pushups. If you're going to be out exploring all day and only here for sleeping, it's perfect. It's in a very quiet neighborhood and 800m (~10 min) to the nearest train (Nakano) station. I loved exploring the yokocho of Nakano mall area, a maze of restaurants, bars and shops and the food truck park at Nakano Park.
The host was very responsive at all hours of the day. Bed was surprisingly comfortable (by Western standards) and shower hot with great pressure. As others said, there is not enough floor space for a bag larger than carry-on size, so be warned. It did get quite cold at night and the unit is not very insulated well.