Very small, juz like the photos depict. Once we lay the additional mattress, walking space is juz a thin line left. We were stranded out during the 1st day & only managed to get in ard 10+pm as we are unable to contact the host. Fortunately a nice Japanese guy helped us, was with us for 2 hrs till we got the key & got up.
Typhoon didn't help & hence half of our stay was rendered useless. Location wise, it was pretty ok. There is also Higashi-Shinjuku stn just rd e corner.
One thing though, Japanese has such a comprehensive train network system that it got so sophisticated