A trip to both countries might run from Tokyo to Kyoto and Osaka, then on to Busan and up to Seoul, or the other way round. Coverage is strong in the cities and holds along most of the Shinkansen and KTX lines, but neither country is in the EU's Roam Like at Home area, and European tariffs usually charge roaming by the day in both. Each also has its own quirks: Korean apps that verify you by phone, and earthquake alerts in Japan.
This guide to an eSIM for Japan and South Korea in one trip compares one Best Asia plan with two country plans, covers the move between them, and explains the apps, alerts and emergency numbers.
Key facts for a Japan and South Korea trip
- One plan for both: the Best Asia plan covers Japan and South Korea among 17 destinations; the Asia plan covers both among 26
- EU roaming: neither country is covered by Roam Like at Home
- Emergency numbers: 119 for an ambulance or the fire service in both; police 110 in Japan and 112 in South Korea
- Embassies: in Tokyo and Seoul, with consulates in Osaka and Busan for some countries
One eSIM for Japan and South Korea, or two plans
The Best Asia plan puts both countries on one eSIM, installed once at home. When you arrive in the second country, the phone should pick up a local network by itself while data roaming is on for the eSIM; if not, choose one manually in your mobile settings. With two country plans, install both at home on Wi-Fi and switch your mobile data line to the second one when you arrive.
Ferries link Busan and Fukuoka, and many flights link the two countries. If the ferry runs its own onboard network, your home operator bills it separately, so keep data roaming off on your home line while you are on board.
Apps, alerts and phone verification
In South Korea, Google Maps shows places but gives limited directions; Naver Map and KakaoMap give full directions and have English versions. Some Korean apps and websites verify users with a Korean phone number, which a travel eSIM does not provide; hotels and tour operators can usually help with those bookings, and messaging apps such as WhatsApp and KakaoTalk work over data.
In Japan, networks broadcast emergency alerts to phones in the affected area, and the Safety Tips app from the Japan Tourism Agency sends earthquake, tsunami and weather alerts in English and other languages. Korean networks also send alerts, usually in Korean, so keep a translation app at hand.
Which plan fits your trip
For a trip through both countries, Telcomia's Best Asia plan covers Japan and South Korea on one eSIM. The Asia plan covers both too; compare the two if your route continues elsewhere in Asia. If most of your days are in one country, a country plan for Japan or South Korea may fit better, with a second plan for the other.
Open the plan details before you buy: they show the duration, the data, whether you can share the connection with other devices, and the Activation line, which tells you what starts the plan's validity.
Before you leave
- Read the Activation line in the plan details, then install the eSIM, or both country eSIMs, at home on Wi-Fi.
- Set the eSIM as your mobile data line, with data roaming on for the eSIM and off for your home line.
- Install Naver Map or KakaoMap for Korea and the Safety Tips app for Japan.
- Keep emergency alerts switched on in your phone's settings.
- Keep each eSIM installed until the trip is over: some eSIMs can be installed only once.
Consular protection: two countries, two sets of numbers
- In Japan, 110 reaches the police, 119 an ambulance or the fire service and 118 the coast guard.
- In South Korea, 112 is the police and 119 an ambulance or the fire service; 1330, the Korea Travel Helpline, assists visitors and can also interpret.
- Embassies are in Tokyo and Seoul, with consulates in Osaka and Busan for some countries. The Telcomia app shows which mission is responsible for you, with address and phone.
- If you are an EU citizen and your country has no embassy or consulate in Japan or South Korea, the embassy of any other EU country must help you on the same terms as its own nationals (Article 23 of the Treaty on the Functioning of the EU).
- Emergency phrases in Japanese and Korean are ready to show on screen in the app.
South Korea travel-safety page →
Questions travellers ask about Japan and South Korea
Is there one eSIM for Japan and South Korea?
Yes. The Best Asia plan covers both countries on a single eSIM, and so does the Asia plan. Two country plans also work, one installed for each country.
Does a Japan eSIM work in Seoul?
Not if it is a Japan plan, which works only in Japan. For Seoul, add a South Korea plan or choose a plan that covers both countries, such as Best Asia.
Do Korean apps need a local phone number?
Some do, for delivery, shopping or certain bookings. A travel eSIM gives you data, not a Korean number, so ask your hotel or tour operator to help with those; messaging apps work over data.
Which emergency numbers work in Japan and Korea?
119 brings an ambulance or the fire service in both countries. For the police, dial 110 in Japan and 112 in South Korea.
The short version
Best Asia covers Japan and South Korea on one eSIM; two country plans may suit a trip spent mostly in one of them. Install everything at home, add Naver Map or KakaoMap and the Safety Tips app, and save 119 for both countries, plus 110 for the police in Japan and 112 in Korea.
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