the hostel is really closed to the station, no need to cross the footbridge, nor stair, nor tunnel, just 3 mins walking is fine. Plenty of Local train to get back to Shinagawa station and even convenience to HND airport.
Also, 3 supermarket within 3 mins walking and family mart is just 10 feet far.
You may find some visitors from europe there, and the japanese staff there is with fluent english (even non-asia accent).
It is really a good choice if you wish to stay a night before taking the early flight from HND. Just a little problem, the room is bit narrow and might keep accidentally hit the wall and make some noises to the next room.