To me, this apartment really is a hidden gem. It's really small (fits a single person), but it has everything you need crammed into that tiny space. The best thing? The location. It's situated basically in the middle of Tsukiji, and within a 2-3 minute walk, you're right inside the outer fishmarket, where all the small shops are - perfect for breakfast! It's also really easy to be first in line to something like Sushi Dai, where you have to line up before the trains start running, because it's only about a 5-10 minute walk away.
And if you want to go to the rest of Tokyo, there's two Metro lines within about a 5-10 minute walk.
The room itself was clean, came with everything I needed, and after my arrival I was greeted by a staff who came to the apartment, to make sure everything was okay, and to show me how the washing machine, aircondition etc. worked.
The only tiny drawback I guess, is the lack of elevators - carrying up heavy luggage can be a pain, because the stairs a really narrow. But it's only something you do for arrival and departure - so honestly, I'm still gonna rate this apartment with all the stars it can get. Highly recommended.