This is there official answer. It focuses on voltage. The Dyson Airstrait straightener, Dyson Airwrap multi-styler and Dyson Supersonic hair dryer - Can I use it abroad/overseas? | Dyson Community. If Japan use the same voltage, then it will work. If it doesn’t then I doubt it will turn on. 

Hi there @maha 

The quick and easy answer here is no. 

The Dyson Airwrap multi-styler, Dyson Supersonic hair dryer and Dyson Airstrait straightener have been precisely engineered for styling at the voltage of the country in which they were manufactured for and purchased in. When considering taking any of these products outside of the country they were manufactured for use in, where the same electrical voltage isn’t applied, they may become inoperable. Please follow the guidance on usage in the guarantee sections of the User guide.

For example. Those products manufactured for use in the United Kingdom operate on 230V and 50Hz (Voltage range of 216.2V to 253.0V), whereas the those manufactured in the United States of America operate on 120V and 60Hz. Due to this difference, a product manufacture for use in one country, may become inoperable in another. 

Can I use an adaptor or an electrical convertor?

We don’t suggest the use of an adaptor or converter to use your device in another country, as that can cause damage to the machine, including permanent damage to the motor. The only Dyson device in our Hair care line that is currently rated for universal use (with the exception of Japan) is our Dyson Corrale hair straightener.

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(Edited by moderator – Title amended) 

Please elaborate on “with the exception of Japan”.  What products will work interchangeably with Japan?

None. That is why they’ve not specified. IN summary, Dyson haven’t tested any converters or adapter. If you use on of these and it doesn’t work, and breaks the unit. Dyson aren’t liable for a replacement under the warranty.  

1. I was asking @Audra, mod and the person who made the statement.
2. I said nothing about an adapter or a converter.
3. To say “none” requires that one dispense with all knowledge of AC power.
4. AC is a variable voltage by nature. US Power for example, oscillates between 70VAC and 169VAC. That is why you see it called 110, 115, 117, and 120 interchangeably. Japanese power oscillates between 59VAC and 141VAC, and is called 100V uniformly. For a well designed power supply, they are virtually identical.  
5. Because of #4, well designed devices have a range/tolerance that is generally pretty wide.  +/-5% minimum (NEC standard), but often +/-10% or more.  For example, 100V RMS isn’t even considered a “brownout” on US power systems. 
6. I just checked my precision oscilloscope and the voltage range is 97-137VAC. Which means it will operate properly in Japan without modification.  And... it cost less than the Airwrap.
7. A step down transformer is precisely what the power company uses to take 7200VAC and deliver 120v/60Hz (US) or 100V/60hz (japan) to your home. There is zero reason to void the warranty when one is using a properly spec’d stepdown transformer.
   
   All that said, @Audra stated that there are exceptions relevant to Japan. I would like to know what these are.

@100VUser this is a community of dyson owners. Of course someone else is going to reply. It’s usually social etiquette to thank them for their input or say nothing. 

Anyways - She’s ALREADY ANSWERED YOU!

“The only Dyson device in our Hair care line that is currently rated for universal use (with the exception of Japan) is our Dyson Corrale hair straightener.”

Bob.

No, she has not.

Is the Corrale NOT rated for Japan?  Or are there other devices that are. The statement is unclear. You did nothing to clarify it.

Late to the conversation as usual.

@100VUser Dyson sell a separate model in Japan. Travel regulations are very strict. 

If you’re after those Dyson products that can be used internationally, give the below a read;

There are some exclusions from this, such as the use of Cordless vacuum cleaners and those other products with an internal battery - Including the Dyson headphone and the Dyson Corrale hair straightener.

Here’s some content to help you get started:

1. The Dyson Airstrait straightener, Dyson Airwrap multi-styler and Dyson Supersonic hair dryer - Can I use it abroad/overseas?
2. How do I use the headphone on a domestic or international flight?
3. Can I use my Cordless vacuum cleaner abroad/overseas?

You’re repeating content that has already been posted, but you did not answer the question.

The statement is:  “The only Dyson device in our Hair care line that is currently rated for universal use {snip} is our Dyson Corrale hair straightener.”

Ok, that is clear. But she inserted “(with the exception of Japan)”

That implies either
a)The Corrale does not work in Japan
or
b) Japan is an exception to “only device rated for universal use”

I would like to know which, and why?

Also, I am not asking about “universal use”.  I am specifically asking about Japan, which has a huge overlap with the US electrical system. So much so that they can safely use the same plug type.