I am here on a Non-Immigrant B Visa with Multiple-Entry.

Before I do my visa run after 90 days, do I need to report to the police or the Immigration Bureau or can I simply do the run?

I've heard there is this law that everybody needs to register / report but it has been only enforced recently.

Thanks in advance.

You only have to report after 90 days under this rule (as stated on tm6 that you fill out upon entry), but as you are never here more than that time it does not apply to you. There is another requirement to report any change of address but it is not usually strictly enforced and if you change hotels they will be reporting you. The last thing they need are thousands of tourists lining up to report hotel changes.

There is another requirement to report any change of address but it is not usually strictly enforced and if you change hotels they will be reporting you. The last thing they need are thousands of tourists lining up to report hotel changes.

Thanks for the quick reply.

What a relief! However, I'm not staying in a hotel but am renting a house with two friends. So it still doesn't apply to me?

No. On each entry you report your address on the tm6 card and only stay 90 days.