Can you leave your luggage at the hotel before check-in?
Yes — almost every hotel and ryokan holds bags before check-in and after check-out, at no charge, and it is a normal thing to ask. Check-in and check-out times themselves are firm, so plan the day around them rather than around the bag. Coin lockers at major stations are the fallback when the hotel is across the city.
Where this answer comes from
Say it in Japanese
Show the card to the staff. The Japanese, how to read it, and the recorded voice.