This is a unique space! It is narrow and tall, with 3 floors. There are lots of beds, so it fits a lot of people, but I was there alone. First and foremost-- It is in a perfect location-- less than 3 blocks from Ueno Station's amazing access to everything (pro-tip: exit out Exit #1, near the central/main gate when you arrive to be closest), on a very quiet block, near many restaurants and konbini, and an easy walk to Ueno Park. That alone was enough for me.
It does sleep quite a crowd, it seems, with bunk beds on 2 floors. I don't see how all those people would fit in the living space, though, honestly: It's just a tiny kitchen and one toilet with a small bath and only a little kitchen amenities like plates and such. There are only 2 chairs downstairs and no table, and a 2-person kind-of-couch/game bed thing upstairs. For a large group, you probably shouldn't expect to hang out there a lot, but again, I don't speak from experience. And westerners, note: While they are on bunk beds, the beds are *not* western beds: they are thin japanese futons placed on the bunk beds. Didn't bug me much, but if you are expecting a mattress, note that there aren't any. Also, the stair treads are very narrow for big western feet, but I just went down sideways :)
All in all it was a fine basic apartment with a unique layout, in a great location. I was happy to stay there.