It's a short walk to the train station, halfway btwn Ueno and Shinjuku on the main (green) line. The trains come frequently, great because Otsuka is a pretty low-key neighborhood, and Ikebukuro is an unscenic 30min walk away.
The space is really small, with nowhere to sit. The bed is a futon mattress up the ladder, so you'll probably keep your bag downstairs. If you're not careful, you'll end up crawling over it every time you use the sink.
The stay itself felt a bit impersonal. I received frequent copy/paste reminders about the late check out policy, and utilities for monthly rentals (I stayed for a wknd). The unit was cold when I walked in; I had to find the heater and figure out how to work it (it's by the bed upstairs and quite loud). I didn't make much trash, but I had to manually sort it to check out.
I know Airbnbs are often investments for people, but some small touches - like separate, labeled trash cans, and preheating the apartment - would make this feel more welcoming.