Could i damge my iphone if i try to charge it in japan(100v) from the US (110v)?

Could i damge my iphone if i try to charge it in japan(100v) from the US (110v)?

No.

All USB ports follow the same standard in any country, which is what is actually charging the phone. Regardless most usb chargers (not all) are universal voltage including the ones that come with iPhones. On the back of the charger you will what it's compatible with. If it says 100v-240v then you are good.

No.

The charger adjusts to all line voltages.