How it works
Self check-in properties typically use either a lobby kiosk where you scan a booking confirmation and passport to receive a room code, or a fully remote process where a door code or smart lock PIN is sent by email or app ahead of arrival. Either way, no one greets you in person, which suits travellers arriving at odd hours far better than a traditional staffed front desk with fixed check-in windows.
What to prepare
Make sure your booking confirmation and passport are easily accessible on arrival, and that you have a charged phone if the process is app-based — a dead battery at 11pm outside a locked, unstaffed hotel is a genuinely bad way to end a travel day. Save any provided support contact number in advance rather than assuming you'll find it on-site.
Trade-offs
The obvious trade-off is no one to ask for recommendations, no luggage help, and no one to sort out an unexpected problem in person — for a first Japan trip or a stay where in-person service matters, a staffed hotel may be worth the difference. For a straightforward overnight stop, self check-in is usually simpler and often cheaper.