Yes, they do.
We carefully make each belt true to size, however please note that humidity and sweat will cause the belt to shrink a little bit over time. It's what we call in Japan "the belt is alive".
We've also had a few rares cases when the belt shrank during transportation from Japan to the customer's address overseas.
Therefore we'd like to kindly ask for a 2cm discrepancy/margin of error.
If you are going to wash the belt then it will shrink. We do not recommend washing the belt, but some people like to do it. Please keep in mind that even if you do not wash the belt, it will naturally shrink from sweat and moist.