True Meaning of “Unlimited”: Japan Prepaid SIM/Pocket WiFi Service Frequent Misunderstanding

One day, I came across a painful message about Japan SIM/WiFi service, saying


In this page, I will try to remove the pain he experienced.


He says: I have exp. with false “unlimited”.


It is quite natural that he should be confused.
Because the term “unlimited” on Japan SIM/WiFi service is very complicated.


Many SIM/WiFi companies in Japan often use the word “Unlimited” on their official websites.
Technically, they might be true, as long as users only use their SIM/WiFi within the limit of “Unlimited.”
But to use it without any stress, you need to read carefully on their service descriptions.


I’ve listed major complaints by people who believed their “Unlimited” is true.
These claims will be useful for you as reference.


  • Data transfer speed gets a sharp decrease once a certain amount of data is used within a certain period of days.
  • Data transfer speed will be slow as many other people use the same service in the same time.
  • Data transfer speed is limited during the peak hours (ex. roughly between 6pm-2am).


If you want to confirm a smooth network, before you actually buying/renting Japan SIM/WiFi, you’d better check it out or ask about it to person in a company.


Good trip starts from good preparation.
Hope your travel in Japan will be memorable.