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Japan is one of the easiest countries on earth to buy a tourist SIM in, which is exactly why a free eSIM is worth having anyway: it covers the hour before you reach the counter. co:sim's free new-user eSIM for Japan is 1 GB valid for 7 days, $0 at checkout, installed before you fly and ready to connect after arrival at Haneda, Narita, Kansai or New Chitose once enabled and within its listed network’s coverage.
This guide covers who it actually suits, which Japanese networks carry it, whether 1 GB survives a week of maps and translation, and what changes about buying a local SIM in 2026.
It is designed as an arrival-sized allowance rather than a replacement for every trip. One gigabyte may cover light maps, messaging, train information and occasional translation for a day or two, but that is a usage scenario, not a guaranteed duration. Video, uploads and background traffic can change it quickly. A 48-hour Tokyo layover might fit the allowance; for two weeks, compare a larger paid plan and use your own usage history to size it.
Scale is part of the argument. Japan took in 3,597,500 foreign visitors in January 2026 alone, with South Korea the largest single source market at 1,176,000, according to JNTO's monthly arrivals release. These are preliminary national arrivals, not a measurement of any airport SIM queue or staffing.
It suits three people in particular. The first is anyone landing at Narita, where the train you want is an hour of decisions away and the reserved-seat machines are easier to work with a phone in hand. The second is anyone arriving after the counters shut — Haneda's international terminal runs through the night, and the SIM desks do not. The third is anyone who simply does not want to hand over a passport for a one-week data plan.
The honest limitation: this is a data-only eSIM. You get mobile data, not a Japanese phone number, so no SMS and no voice calls over the plan. Every messaging app works normally, which is what most travellers actually use.
The current selected co:sim Japan 1 GB / 7-day SKU lists KDDI/au and 5G support, not access to all four Japanese operators. Check the exact plan’s network list before claiming or buying, because another Japan SKU may have different terms. The national comparison below gives background on Japan’s networks; it does not describe a choice of four networks on this free card or guarantee its speed.
Japan's coverage is excellent by any standard, but its 5G story is more modest than the marketing suggests. In Opensignal's April 2026 Japan report, SoftBank users saw the fastest average download speeds at 65.1 Mbps, ahead of au at 60.7 Mbps, docomo at 55.7 Mbps and Rakuten Mobile at 39.6 Mbps. SoftBank also won Time on 5G outright with 27.4%, eight percentage points clear of au.
Read that second number carefully. Even on the strongest network, SoftBank users in that report were actively on 5G roughly a quarter of the measured time; that is not a forecast for every phone, operator or roaming plan. That is not a problem for maps and messaging, and it is a useful expectation to set before you compare a "5G eSIM" against a "5G SIM card" as if the label decided anything.
Where coverage genuinely thins is predictable: mountain trails, the deep valleys of the Kumano Kodō, and stretches of rural Hokkaidō. Do not assume any particular village or mountain station has uninterrupted service. Download offline maps for hiking days regardless of which plan you carry.
For a week of light navigation and messaging, 1 GB may be workable, but it is not a guaranteed daily budget. Map downloads, translation-camera use, images and background traffic vary by app and settings. Download maps and language packs on Wi-Fi before leaving, check your phone’s per-app cellular usage, and watch the remaining allowance during the trip. A short layover usually needs a different allowance from a full week of frequent navigation.
Video and photo uploads can exhaust a small allowance quickly; resolution, compression and app settings change the amount used. Turn off cellular photo backup and automatic downloads before arrival, then use Wi-Fi for large transfers. That reduces avoidable usage but does not guarantee 1 GB will last a week. If you plan to stream, work from a laptop or share data regularly, size a larger paid plan instead of relying on the trial.
If only the data runs out and the card remains eligible with its validity still open, buy a top-up offered in your co:sim account without reinstalling the profile. Eligible unused cards can also top up before first connection. Once validity has expired, a top-up cannot revive the card; choose a new paid Japan plan instead. This gives you an online option while in Kyoto without having to return to an airport counter.
FREEClaim the free eSIM for JapanA physical airport SIM can be useful if its services and terms fit your trip, but compare its actual current price, allowance and identification requirements. For a longer stay, co:sim also offers paid Japan plans that you can choose before departure; there is no reason to assume an airport SIM is always the better next purchase. Check counter or vending-machine availability for your arrival terminal and time rather than relying on all-night sales.
There are still practical reasons to prepare the trial before departure: you can have the profile and instructions ready rather than arranging them at a counter. Using data after arrival requires an eligible device, the correct selected data line and settings, remaining validity and a successful connection in a listed network’s coverage. Preparation does not guarantee a connection at the gate, before a queue or at any particular minute. Local-SIM identification requirements are a separate issue to check for the actual product.
Japan’s July 2026 MIC implementation paper describes an amendment passed on 22 May and promulgated on 29 May 2026, with commencement on a date set within a year of promulgation. It discusses extending identity checks to data SIMs, including the proposed scope for SMS-capable data SIMs and possible IoT exclusions. Those scope details are presented as matters for implementation, not proof that every tourist data SIM already needs a passport. Check the current rules and the actual seller’s requirements before buying a local contract.
The selected co:sim trial is a roaming data profile, and the current catalog states no passport-based eKYC for that SKU. This is a product condition, not a general legal exemption for all eSIMs bought abroad. Claiming the gift still requires a new-customer sign-in and a valid payment card for verification, with no charge.
The order is the whole point: install at home on Wi-Fi, activate on arrival.
co:sim TeamSettings → Cellular → Add eSIM. On most Android handsets: Settings → Network & internet → SIMs → Add eSIM.Installing needs an internet connection, which is why doing it at the airport in Japan is a chicken-and-egg problem people run into every week. Check the activation deadline at checkout and in your order, and install and activate before it. Even an installed card may be cancelled if still unactivated after that deadline. The selected trial’s seven usage days start at first connection in Japan; other SKUs may start at first installation or purchase, so read their own terms.
Travelling on to Seoul afterwards? The Japan free card does not cover South Korea. A paid Asia 14 regional plan currently lists both Japan and South Korea among its covered destinations, so compare its exact allowance, networks and billing-start rule if you want one profile for both legs.
Prepare before departure: claim the trial, allow time for fulfillment, and follow its installation and activation instructions. After arrival, test data within the listed network’s coverage.
Browse co:sim's Japan eSIM plansNo, and the distinction matters at checkout. co:sim's new-user free eSIM is one promotion funded across several separate products. One of them is a regional card covering 33 European countries and territories on a single profile. The Japan version is its own single-territory plan: it works throughout Japan and nowhere else, with no roaming into South Korea, Taiwan or anywhere in between. Turkey, Moldova, Singapore, Malaysia, Indonesia, Thailand and South Korea each have their own separate card in the same way. The offer itself can be claimed once per new customer, so you are choosing which country to take it for rather than collecting several. Pick the country where you actually land first, or where you will spend the most days without other connectivity.
The trial can provide mobile data on rail journeys where its listed network has signal, but it cannot guarantee continuous service on every Shinkansen route or in every subway tunnel. Underground coverage, terrain, train movement, congestion and the handset all affect the connection. Using national mobile infrastructure does not mean this roaming profile can use every Japanese operator or match the experience of any local phone in the same carriage. Its selected network is KDDI/au; check the current plan details for your trip. Keep train bookings, ticket details and essential translations available offline, and download maps before a long rail day. If you need to join a call on the train, allow for interruptions and consider postponing it until a stop. A 5G label is a capability, not a promise that the whole journey stays on 5G.
The trial stops carrying data when its 1 GB is exhausted or its seven-day usage period ends, whichever comes first, without automatic renewal or a usage bill. This selected trial starts counting on first connection in Japan, not at purchase or installation; still respect the separate activation deadline shown in the order. If only the data is depleted and the card remains eligible and valid, buy one of the top-ups shown in your co:sim account. It adds data to the same profile without reinstalling or scanning a new QR code. Eligible unused cards can also top up before first connection. Reloadable does not mean renewable: a top-up cannot restore expired validity. After expiry, choose a new paid Japan plan for the rest of the trip. That separate purchase may need its own profile and QR code; it does not promise reuse of the trial or an uninterrupted switch.
No, if your particular phone supports the required combination of active SIMs. Keep your home SIM installed, select co:sim as the mobile-data line, disable home-line data roaming and turn off automatic cellular-data switching. On iPhone, check these options under Settings → Cellular; Android menu names vary by manufacturer. Saving several profiles and running two lines at once are different capabilities, so verify the exact model and regional version before travelling. Your usual number may still handle calls and texts if your home carrier supports roaming there, but those services can incur charges even with data roaming disabled. A bank SMS is therefore not guaranteed by the co:sim data plan; check home-carrier service and pricing in advance. The trial adds data connectivity without porting or replacing your original number.
Yes, hotspot works, and it is the usual way a couple stretches one plan across two phones. The catch is arithmetic rather than policy: a tethered device draws from the same 1 GB, and laptops are considerably hungrier than phones, because background sync, cloud backup and software updates will empty a gigabyte quickly the moment they see an unmetered-looking connection. Two people checking maps and messages will not notice the difference; one person opening a work laptop will. If you plan to share deliberately rather than occasionally, a paid Japan plan with a larger allowance is the sane choice, and the free trial becomes the thing that gets you both online at the airport while you decide. Turn off automatic photo backup on any device you tether before you start, and check the hotspot setting is actually pointed at the co:sim line rather than your home SIM.
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