According to the specifications on page 28 (last page) of this document,
https://panasonic.jp/p-db/contents/m...8373674815.pdf
these devices are designed for 100 volts at either 50 or 60 Hz (half of Japan is 50 Hz and the other half is 60 Hz). US/Canada voltage is about 120 volts at 60 Hz.
Look for a step-down transformer that will take 120 volts / 60 Hz to 100 volts / 60 Hz to assure no issues with the device. A quick Amazon search showed a device for approx USD $30 that will make the adjustment from US/Canada 120 volts to Japan 100 volts or visa versa at 200 watts, and for example, the humidifier model F-VXR90 uses 88 watts max so well within the capacity of the 200 watt converter.