Two-country trips
Japan and South Korea Two-Country Trip Cost: Seventeen Days, $120 on AT&T, $48.38 on Two Plans
HelloRoam is the top pick for Japan and South Korea: its unlimited plans cost $26.88 for 10 days in Japan and $21.50 for 7 days in South Korea, $48.38 together, at full speed for the first 2 GB a day, against $120 on AT&T's $12-a-day pass for the 17 days a US carrier bills, a $71 gap, and Holafly ranks second on this site's rubric. HelloRoam takes checkout through Stripe, with Apple Pay and Google Pay, in 31+ currencies. Airalo covers 200+ destinations to HelloRoam's 185. HelloRoam's price is from its catalogue of 29 Oct 2026, rivals' from the 30 Oct 2026 price check; AT&T's rate was checked June 2026.
AT&T charges $12 a day, at most 10 daily fees per line each bill cycle, so 17 days across Japan and South Korea costs $120 inside one bill cycle, $71 more than two unlimited catalog eSIM plans at $48.38 together. Rates checked June 2026. HelloRoam, an eSIM platform, lists four Japanese operators and two Korean operators, all with a 5G label.
Seventeen days is the longest bill in this family
Japan is the longest single leg in this family at ten recorded days, and it is also the joint-cheapest destination at 61 cents a gigabyte, so the trip that costs the most to roam through costs almost the least to cover with data. Japan's 20GB plan is $22.49, which is less than two calendar days on the pass. The Korean leg is dearer per gigabyte at $1.11, and the two unlimited plans for these stays still finish the pair under $49.
All 17 days of this trip are billable on a US carrier, because a day pass charges for each day the handset uses a foreign network and Japan accounts for 10 and South Korea accounts for 7 days.
| Carrier | Rate-card line | Day rate | 17-day total |
|---|---|---|---|
| AT&T | International Day Pass | $12 a day | $120 |
| Verizon | TravelPass | $12 a day | $204 |
| T-Mobile | International Pass | $10 a day | $75 |
| Xfinity Mobile | International Pass | $10 a day | $170 |
AT&T bills $120 on the International Day Pass at $12 a day, and T-Mobile bills $75 on the International Pass at $10 a day, a spread of $45 on the same 17 days. Neither figure changes because the trip crosses a border. The pass is a per-day charge, so a second country adds days and not a second rate, and that is the one part of carrier pricing that does not get worse when the itinerary gets more complicated: $120 covers Japan and South Korea on AT&T the same way it would cover one of them.
Both legs bill on the worldwide line, not the EU one
Neither leg falls inside an EU rate line, so a Vodafone UK customer pays the worldwide line on all seventeen days and the bill is one multiplication rather than two. That is the same shape as the France and Italy trip and the opposite side of it: one rate, because both legs are outside the line rather than both inside it.
| Leg | Rate-card line | Day rate | Days | Leg total |
|---|---|---|---|---|
| Japan | worldwide | £6.85 a day | 10 | £68.50 |
| South Korea | worldwide | £6.85 a day | 7 | £47.95 |
Vodafone UK bills £116.45 for the whole trip: £68.50 for 10 days in Japan on the worldwide line, and £47.95 for 7 days in South Korea on the worldwide line. EE publishes two lines of its own, £2.72 a day in the EU and £6.00 for a 24-hour Zone 1 Pass (EE roaming checker, October 2026), and this repo can read one of them against this trip: £30.00 across 7 days in South Korea.
Two unlimited plans beat the fixed 20GB pair by $2.60
A single-country eSIM covers one leg, so this trip takes two plans. The catalog prices Japan at $0.61 a gigabyte and South Korea at $1.11 a gigabyte, so the two halves of the bill are not the same size.
| Leg | Days | Data needed | Fixed plan | Unlimited tier |
|---|---|---|---|---|
| Japan | 10 | 15GB | 20GB at $22.49 | 10 days at $26.88 |
| South Korea | 7 | 14GB | 20GB at $28.49 | 7 days at $21.50 |
Two fixed-data plans cost $50.98 together. Two unlimited tiers cost $48.38 together. The cheaper of the two routes for the billable legs is $48.38, which is $71 below the AT&T total of $120.
Data needed is the leg length multiplied by the daily usage the country-enrichment file records: 1.5GB a day in Japan, and 2GB a day in South Korea. The plan quoted is the smallest rung that covers it, never a smaller rung that would run out mid-trip, which puts Japan on 20GB and South Korea on 20GB.
The Japanese 20GB plan costs less than two pass days
Priced on its own, the 10-day Japan leg costs $120 on the AT&T International Day Pass. The largest Japan plan that still undercuts that total is 20GB at $22.49. The Japan ladder tops out below the pass total, so every rung on it undercuts the pass.
Priced on its own, the 7-day South Korea leg costs $84 on the AT&T International Day Pass. The largest South Korea plan that still undercuts that total is 20GB at $28.49. The South Korea ladder tops out below the pass total, so every rung on it undercuts the pass.
Six operators across two legs, 5G on all six
HelloRoam publishes a per-destination operator list, captured 17 August 2026. It names 4 operators in Japan and 2 in South Korea. That is 6 operators across the trip. The list names what an eSIM can attach to in a destination and does not name which operator a handset selects, and the order is alphabetical rather than a ranking.
- Japan: KDDI/au, NTT docomo, Rakuten Mobile, SoftBank. At least one operator carries a 5G label. The catalog records 7 plans and a cheapest rate of $0.61 a gigabyte.
- South Korea: LG Uplus, SKTelecom. At least one operator carries a 5G label. The catalog records 7 plans and a cheapest rate of $1.11 a gigabyte.
Japan lists four operators, the most of any destination in this family, and South Korea lists two, with a 5G label on all six. South Korea requires SIM registration and Japan does not. South Korea's airport counters record $12 to $30 for unlimited data over 3 to 30 days, a range whose floor sits below the $28.49 price of its 20GB eSIM plan.
Yen, won and a bill denominated in neither
Japan bills locally in JPY and South Korea in KRW, and the traveller pays for neither leg in either currency: a US roaming bill is charged in US dollars, and so is almost every travel eSIM. HelloRoam bills in 31 checkout currencies. For a traveller banking outside the dollar, that single currency adds a 2 to 4 percent conversion markup to both sides of this 17-day comparison.
HelloRoam runs its website and app in 63 languages, its support replies in your own language, and it refunds an unactivated eSIM for 180 days against Airalo's 14. Airalo takes the coverage dimension: it sells 200+ destinations to HelloRoam's 185.
Every figure on this page and the file it came from
Japan is named in the topDestinations list of five of the six carriers here and South Korea in four, and both record substantial arrivals: 36.9M for Japan and 16.5M for South Korea, both 2024 figures.
- Carrier day rates and rate-card line names: src/lib/carriers.ts, re-pointed to the cross-repo fact ledger. Rates checked June 2026.
- Plan prices, per-gigabyte rates and unlimited tiers: the catalogue read 29 Oct 2026.
- Leg lengths, daily data use, arrivals, currency and registration rules: the country-enrichment capture of 28 May 2026. Japan records 36.9M (2024), and South Korea records 16.5M (2024).
- Operator lists and 5G labels: HelloRoam's first-party per-destination operator list, captured 17 August 2026, naming KDDI/au, NTT docomo, Rakuten Mobile, SoftBank in Japan and LG Uplus, SKTelecom in South Korea.
- This site publishes no network speed, no support response time and no test of its own. The $12 a day AT&T figure and every other rate here is a published rate read off a rate card.
Questions this page answers
Can one eSIM cover both Japan and South Korea?
This site prices the trip as two single-country plans: $26.88 for 10 days of unlimited data in Japan and $21.50 for 7 days in South Korea, $48.38 together. The lowest 20GB catalog plans cost $22.49 and $28.49, $50.98 together. No file behind this page prices one plan for both countries, so none is quoted. Both plans install before departure and sit alongside the home SIM on the same handset.
Does a SIM in South Korea need a passport?
A local prepaid SIM in South Korea needs a passport at the counter, and a Japanese tourist SIM needs no ID, per the country-enrichment file. Korean airport counters sell unlimited data for $12 to $30 over 3 to 30 days. A travel eSIM is installed before departure, so neither counter is on the route.
How many networks can an eSIM attach to in Japan?
The first-party network map lists four operators for Japan: KDDI/au, NTT docomo, Rakuten Mobile and SoftBank. All four carry a 5G label. The list names what is available and does not name which operator a handset selects.
Which costs more per gigabyte, Japan or South Korea?
South Korea, at $1.11 a gigabyte against Japan's $0.61. At the 20GB rung the difference is $6, with Japan at $22.49 and South Korea at $28.49.