Japan eSIM for a 30-day stay: how it differs from a short trip

How much data 30 days in Japan takes

A month in Japan: a resident's rhythm, not a tourist's

People staying thirty days usually have one of a few reasons: a short Japanese language course, remote work from Tokyo or Fukuoka, visiting relatives or a partner, or slow travel using one city as a base. The common pattern is renting an apartment or share house in one or two cities and repeating the same routes daily.

With a fixed home, night-time internet comes from the apartment's fibre rather than the SIM, and mobile data is mostly for use outside. So the 31 GB normal figure for thirty days may be higher than reality for someone who mainly uses home Wi-Fi. Check whether your lodging has permanent Wi-Fi before buying a big pack.

Three levels for thirty days

The estimate table gives thirty days as 14, 31 and 65 GB for light, normal and heavy use. The comparable Japan packs are 20 GB for light, 50 GB for normal, and for heavy use beyond 50 GB you need to combine methods, such as the 50 GB pack alongside home fibre or an extra pack.

• Light (about 14 GB): the 20 GB, 30-day pack is enough and suits people who mainly use home Wi-Fi.
• Normal (about 31 GB): the 50 GB pack, with about 19 GB of margin.
• Heavy (about 65 GB): beyond 50 GB, so use home fibre as the base with mobile data as a supplement, or a 3 GB daily plan that totals about 90 GB over the month.

The 180-day pack, if you will come back

Japan has a 50 GB pack with 180-day validity, listed on the NTT docomo network only. This may interest someone who knows they will return within six months, such as a student on a continuing course or someone who flies for work. It is a decision worth reading the plan page for carefully, especially the network and usage terms.

Working remotely from a laptop on mobile data

If you tether a laptop for work, a one-hour video meeting uses a fair amount of data, and large file uploads burn data quickly. Check on the plan page whether your version allows tethering, and do not make mobile data your primary line for work that cannot drop. Use the apartment's fibre as the main connection and keep the eSIM as backup.

What a travel eSIM cannot do in a month

• No Japanese number and no SMS, so it cannot receive verification codes sent by SMS. Use your Thai SIM kept on for OTPs.
• Long-term rentals, opening a bank account or joining some services in Japan often need a Japanese number and residence documents. A travel eSIM is not the answer to that.
• If you intend to stay longer than your travel status suits, check the rules with official Japanese sources, not blogs.