The hotel asked to make a copy of my passport when I checked in. Is this necessary?

When a foreigner not residing in Japan stays at a hotel, the hotel is required by law to enter into a guest register the nationality and passport number of all staying guests. That is why the hotel staff will ask for your passport and keep a copy of it. This is meant for security purposes, such as to prevent terrorism. We ask that all visitors to Japan cooperate so that they can travel with peace of mind.