Excellent place. Recommended for not more than 2 pax because it can be a bit of a squeeze. Bed is a bit small but fits me and my friend ok since we are both 2 small asian girls. Bed is comfortable and clean. Towels were provided for each of us, both bath and face towel.
Toilet bowl has a bidet function, which i love. Hot water is readily available in the showers and the apartment is cosy enough.
Great place to stay. A bit of a distance from Shinjuku station but not a biggie since we were okay with walking. No lift up to the apartment (which is on the 3rd floor), so you'd have to be ok with lugging your bags up narrow flights of stairs.