It’s good, small but nice and private. Cheap too. Nice cooking facilities and fridge. Wonderful location subway almost literally a skip and a jump away. Bathroom has hot water in the bath (it does have one admittedly small but this IS Japan after all right?). WiFi access is a nice plus, fast and no fuss.
Only caveat: it IS a little cold downstairs, but the sleeping place has a cozy warm bed with heater, so it didn’t bother me. The bunkbed-style setup might not suit older or less mobile travelers, but for younger people it’s fine and I found it novel and quirky.
I would say it’s excellent for the younger budget traveler, and while critically speaking it wasn’t perfect, it’s a nice little place, comfy sleep, great location, affordable especially for Tokyo, I would definitely book again.