Japan Travel Fixes
Why do hotels ask to see my passport at check-in?
Japan's Hotel Business Act requires accommodations to check and keep a copy of a foreign guest's passport. It isn't a specific hotel's quirk — without it, some properties will refuse to check you in at all.
This isn't hotel-specific policy, it's a legal requirement, so there's nothing suspicious about being asked.
Staff will typically photocopy your passport or note down its number.
If you've lost your passport, some hotels won't let you check in that day, so it's worth keeping it on you at all times.