Concerned about Tokyo hotel reservation

Made an online reservation Today directly on the hotel's website.

Received an email confirming 7 night stay commencing 11th May - included a confirmation number - and stating that I could cancel without penalty up until 6:00pm local time on 11th May.

However, at no stage during the booking process was I asked for a credit card number to guarantee the reservation...

Couple of questions:

1. Is this normal for hotels in Tokyo ?

2. Am I taking a risk - I won't arrive until midnight after a long Intl flight and I would hate to get there only to find that they've given my room away to somebody else...

3. How can they have a cancellation policy when they're not even taking a credit card number during the booking ?

Thanks
Mike

Send an confirmation email to the hotel stating your estimated arrival time 5 days prior to actual arrival date.

I usually do so in case I won't arrive before 8PM and no problem happened to me by now.

This is normal anywhere in Japan. It is actually one of the best things I like about Japan; an example showing that values like "trust" and "integrity" still mean something.

If you made the booking they trust that you are going to be there. If you end up not going you should have the integrity to make arrangements to pay the penalty despite not having placed a collateral.

In short, you are not taking a risk, although it is a good idea to let them know that you'd be arriving late.

Where is the hotel's website?

I could cancel without penalty up until 6:00 pm local time on 11th May.

As is suggested by cc, you had better inform the hotel of your possible late arrival.
If you do not show up by 6:00 pm, you may be deemed to have canceled the reservation unless you have made a notice.
(It sounds to me a rare case that you can cancel a hotel booking up until such a late timing without a penalty. Some hotels demand a penalty on the 2nd day before.)

at no stage during the booking process was I asked for a credit card number to guarantee the reservation...

I suppose it is common in Japan that you are neither required a charge nor identified strictly for booking a hotel / an inn, especially when you apply directly.
Please confirm that your credit card will be accepted at the hotel. (Japan is not so a credit card society as U.S.A.)

I have also recently made a reservation at a hotel in Shinagawa. I specified my check in time as 25:00 as I am only scheduled to arrive Haneda at 11PM. Do you think I should still send the hotel an email to confirm my reservation? I'm concerned the hotel might mistake the confirmation as cancellation or it might create some doubt on my reservation.

25:00?
you mean 01:00 or 24:00?

25:00 is often seen in Japan, especially in television schedules. It actually means 01:00 the next day, but it's used to ensure correct interpretation of the 1am time.

Yes, it's 25:00, or 01:00 the following day. I have specified 25:00 as my checkin time for my hotel reservation on 15 June, it means my eta is 01:00 16 June.

Thanks for everybody's feedback - it has put my mind at rest!

I also received a very nice email back from the hotel (Shinjuku Washington) this morning - they reconfirmed my booking, stated that they did not need a credit card at this stage and said that they will expect to see me at midnight.

Very professional!