Japan Travel Fixes
I don't understand how to use a coin laundromat
It's simple — insert coins (or a dedicated card) and the machine runs. Some machines dispense detergent automatically, while others expect you to bring and add your own.
Machines with built-in detergent dispensing are usually labeled in Japanese ("洗剤自動投入"); if you don't see that label, you'll need to buy and add detergent yourself.
If you're short on coins, look for a change machine on site, or break a bill at a nearby convenience store beforehand.