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One trip, two ways to buy the data
If it’s a week in Tokyo followed by four nights in Seoul, put the expected data for each leg beside the prices below. You can then decide whether the flexibility of one profile is worth more to you than the saving from managing two.
The examples below use our current fixed-data offers, rechecked on 31 October 2026. Prices are in AUD, before any eligible discount. These are planning examples, not measured usage from a trip.
| Option | Data and validity | Total price | The trade-off |
|---|---|---|---|
| Japan and South Korea regional plan | 10GB shared across the two countries; 30 days | A$64.95 | The same remaining allowance is available at either stop. |
| Japan 5GB plus South Korea 5GB | 5GB in each country; each plan valid for 30 days | A$32.90 | Unused Japan data cannot become extra Korea data. |
| Japan 10GB plus South Korea 5GB | 10GB in Japan and 5GB in Korea; each valid for 30 days | A$37.90 | More room for the longer Japan leg, with two separate profiles. |
Two 5GB country plans cost A$32.05 less than the 10GB regional plan. The trade-off is where you can use that data: you get 5GB in each country, rather than 10GB to use in either.
Three itineraries that change the answer
A reasonably even split
Suppose you allow 4GB for Japan and 4GB for Korea. Two 5GB country plans give each leg 1GB of spare room. If your phone can store both profiles and you’re comfortable selecting the right data line at each arrival, the A$32.90 option fits this example well.
A longer Japan stay and a short Seoul stop
If you expect to use 7GB in Japan and 2GB in Korea, a 5GB Japan plan is too small even though you only need 9GB overall. Japan 10GB plus Korea 5GB costs A$37.90 and covers that split. The regional 10GB also covers the total, with one profile to manage and the freedom to use the remaining data in either country.
You genuinely don’t know the split yet
If the schedule is flexible, a shared allowance can be useful. You can spend more time in one country without stranding most of your purchased data in the other. Decide whether that flexibility is worth the price difference to you. One profile is simpler, but it doesn’t guarantee that the phone will reconnect instantly at the border.
Count validity from the first stop
The selected regional 10GB plan starts on first network connection and has a 60-day window to start after purchase. Its 30-day validity then runs across the trip; arriving in Korea does not start a fresh 30 days.
The country-specific 5GB offers in this comparison also have 60-day start windows and begin on first network connection. Each has its own running validity. Check the selected offer before buying because other plans on the same destination page can have different start windows.
Our setup advice is to buy before you fly, save the setup email, then install or activate after arrival using steady airport Wi-Fi. If airport Wi-Fi won’t connect, wait for hotel Wi-Fi or another trusted steady connection. For separate plans, follow the corresponding country’s setup email at that arrival.
Check your phone and the services you actually need
These examples are data-only. They don’t supply a Japanese or Korean phone number, ordinary carrier calls or SMS. App calls and messages use data, but an app asking for a local number is a different requirement.
Check that your phone is compatible and unlocked, and that it can store the profiles you want. Storing two profiles and keeping two lines active are different device capabilities. Keep the unused travel profile off and deliberately select the current country’s data line.
The selected Japan 5GB and 10GB offers list DOCOMO. The regional product lists supported networks in both countries. Use the selected plan’s current network details; buying the regional plan doesn’t mean it uses exactly the same networks as buying the two country plans. Hotspot use also depends on the selected offer, local network and phone.
When roaming or a local SIM deserves a look
Check your Australian carrier’s included destinations, allowance and total trip cost. Roaming may be the easier choice if it already includes enough data and the calls you need. If a service requires a local phone number, check a local SIM’s registration, number and calling terms rather than buying another data-only plan and hoping it solves the problem.
For the next step, compare the regional offers, or compare Japan and South Korea separately. The combined-trip data guide helps you budget the allowance before choosing.
Sources
Offer prices, country coverage, start rules and network notes were checked against the linked live SIM Shop products on 30 September 2026. Always confirm the exact selected plan at purchase. No network speed or border-handover test is claimed.
