North American Appliances in Japan

For cellphone and laptop chargers, what should I bring to make sure I can use it in Japanese outlets without damaging it? An adapter?

Also, I have to bring a flat iron with me. Label says 120v 60Hz 0.35A 35W. It has polarized teeth. Will I be okay using this there?

Thanks in advance.

Essentially nothing, I brought over an Iron, camera charger, laptop when I first moved over to Japan, no adapters, converters or nothing, and they all still work today.

The only thing you "might" need is if you have a three prong item, Japan uses two prongs, so you would need a very simple adapter for three prong to two prongs. Otherwise if your plugs are already two prongs nothing else is needed.

Check to see if your cellphone and laptop chargers cover the range from 100-240V 50-60Hz; any modern charger should but you need to make sure.
Your iron might work or not work, but I would avoid using it as it is always a bit more critical with things that heat up; especially as you must likely use it with a plug converter without the middle prong (earth) as few wall sockets in Japan have that 3rd prong.

As others have mentioned, your laptop and cellphone chargers are probably designed to work worldwide and will probably be fine. Just check the input voltage that is listed to be sure.

Your flat iron on the other hand, and anything that heats up or has electronic timers and was not designed for worldwide use, will not work as normal on the reduced voltage. Most likely, the flat iron will not get as hot as normal. If you are travelling you could consider getting a travel flat iron, or if you will be living in Japan then just buy a new one over here.

Are the outlets in Japan wider in one to fit the wider plug of U.S. design?

Yes, modern outlets accommodate polarized plugs. You may run into older outlets where both receptacles are the same size, but in my experience my polarized plugs still fit without any problems.

When I moved to Japan I brought a flat iron with me, and I can say I haven't noticed any difference from when I used it in America and in Japan.

YMMV

for laptops or cells

conair company has chargers,

in japan electronic stores have converters cheap like 10 bucks

Thank you everyone.

I'm just there for vacation, so I'd rather use the flat iron I have if it's possible.

When I moved to Japan I brought a flat iron with me, and I can say I haven't noticed any difference from when I used it in America and in Japan.

Expresstrain,

Do you mean iron (for clothes) or flat iron (for hair). From what I understand, a clothes iron that doesn't reach its peak temperature isn't the same situation as flat iron that can't reach its peak temperature.

in japan electronic stores have converters cheap like 10 bucks

I presume you are referring to plug adapters (which you won't need unless you have a grounded 3 prong plug) rather than converters. Converters that upconvert from 100v to 120v are a fair bit more expensive than $10, and not commonly carried in electronics stores in Japan.

I'm just there for vacation, so I'd rather use the flat iron I have if it's possible.

Its probably fine to use. I would just expect that it may take longer or be less effective at straightening your hair.

I'd definitely recommend getting a travel flat iron. Neither of my flat irons worked very well in Japan. The low voltage meant they heated up to a "mildly warm" heat at best. They were practically useless when it came to straightening my hair.

Needless to say, I was disappointed with all of my travel photos because I was "the scruffy haired one" in all of them :O