Two different questions, two different answers: a short-term data eSIM for a trip to Japan, or a monthly SIM plan if you actually live here. Both are ranked the same way — official prices only, by real total cost, never by which provider pays us.
It's the English section of SIM実額ナビ (SIM Navi), a Japan-based site that compares mobile data options by their real, all-in cost rather than the advertised headline price. This section covers two different needs: short-term eSIM for tourists, and monthly SIM plans for residents of Japan.
No single provider is favored. Some links on this site are affiliate links, and we disclose that on every page, but whether a link is an affiliate link never changes where a plan is ranked — ranking is always by calculated cost alone.
Every price shown is checked against the provider's own official page, with a link to that source and the date we checked it. Carriers change prices and promotions often, so always confirm the current terms on the official site before signing up.
Go to Visiting Japan (eSIM for tourists). It ranks short-term data eSIMs by real cost for your trip length and daily data use, with no Japanese phone number or residence required.
Go to Living in Japan (SIM for residents). It only ranks carriers that explicitly state, on their own official site, that they accept applicants using a residence card — never a guess.