Roaming vs SIM card vs eSIM: I priced 5 days in Japan three ways
You land at Narita, clear immigration, and now you need data. There are three ways to do it — turn on roaming with the carrier you already pay, buy a physical SIM from one of the counters in the arrivals hall, or install a travel eSIM before you left home.
I priced all three for the same trip: five days in Japan, one phone, moderate data use. The spread was not what I expected:
- Cheapest: HK$40. Dearest: HK$340. Same trip, same amount of data, 8.5x apart.
- The airport counter is the worst-value place on the list — not by a little, by 2.5x against the same kind of SIM sold in town.
- But the cheapest option is not always the right one, and I'll say clearly when it isn't. The real difference between these three isn't the price. It's what each one does to your existing phone number.
Here is the whole picture in one table, then I'll walk through each option and what it actually costs you.
The five-day price table
| Option | Listed price | In HKD | Data for 5 days | Keeps your number |
|---|---|---|---|---|
| Travel eSIM — 1GB/day | HK$40 | HK$40 | 5GB total | No — data only |
| Travel eSIM — 2GB/day | HK$54 | HK$54 | 10GB total | No |
| Travel eSIM — 5GB/day | HK$73 | HK$73 | 25GB total | No |
| Travel eSIM — unlimited/day | HK$87 | HK$87 | No daily cap on high-speed data | No |
| Japan SIM bought in town (IIJmio 3GB/7 days) | ¥1,600 JPY | HK$79 | 3GB total | No — and you lose your own |
| Japan SIM, longer stay (Sakura Mobile 3GB/30 days) | ¥3,000 JPY | HK$148 | 3GB total | No |
| Roaming — China Mobile Japan 5-day package | ¥108 CNY | HK$126 | Unlimited, 384kbps after 3GB/day | Yes |
| Roaming — CMHK GO! Pass 7GB/30 days | HK$188 | HK$188 | 7GB total | Yes |
| Airport counter — SoftBank Global Rental 3GB/5 days | ¥3,960 JPY | HK$196 | 3GB total | No |
| Roaming — CMHK Day Pass × 5 | HK$48 each | HK$240 | 5GB total | Yes |
| Roaming — CMHK Freedom Zone, daily rate × 5 | HK$68/day | HK$340 | 1GB/day full speed, then 512kbps | Yes |
All figures are list prices on the date above, before any promotion. Every roaming plan listed requires an active account with that carrier — there is no walk-in option.
1. Only the roaming rows keep your phone number alive. Everything else is data-only — no SMS to your usual number, which means no bank verification codes, no delivery apps, no two-factor logins.
2. "Unlimited" means a different speed floor at every seller: 256kbps here, 384kbps on China Mobile after 3GB/day, 512kbps on most Hong Kong roaming plans. Those all sound similar and are not: 256kbps will carry maps, WhatsApp and email. It will not carry a video call.
3. The airport counter is not just expensive, it costs you time — passport, unlock check, APN settings, 10 to 30 minutes standing in the arrivals hall.
Option 1: Roaming on the carrier you already pay
This is the only option that changes nothing about your phone. Same number, same apps, messages and calls arrive exactly where they always did. You flip one switch and it works.
If your number is from mainland China — China Mobile sells a Japan multi-day package at ¥108 CNY (about HK$126) for five days of unlimited data. Be aware that the discount which ran through most of 2026 ended on 1 October, so ¥108 is the list price again — you may still see ¥59.5 quoted on older pages and it will not be honoured.
Buy it before you fly (text GMHDJPL5 to 10086, or order through the 10086.cn roaming site) or you fall back to the standard rate of ¥3 per 3MB, capped at ¥30 a day — five days comes to ¥150 CNY, about HK$175. Either way the throttle is the same: after 3,072MB in a single day you drop to 384kbps until midnight Beijing time, which is one hour behind Japan. Your 8pm in Tokyo is 7pm on their clock, so the ceiling resets an hour after your day ends.
If your number is from Hong Kong — CMHK is representative of the market. Day Pass is HK$48 per 1GB / 24 hours, and you can hold up to fifteen unused ones, so five days costs HK$240. The Freedom Zone daily rate is HK$68/day for the first 1GB then 512kbps, which over five days comes to HK$340 — the most expensive line in this whole comparison for the least data. Both of those are priced for convenience, not value. The value option is GO! Pass: 7GB valid 30 days for HK$188, which covers the five days and leaves the balance usable later.
I've used China Mobile and CMHK as the worked examples because they're the numbers I could verify today. If your carrier is elsewhere, the same arithmetic applies — check the multi-day package price against its daily rate, and check whether the throttle is per-day or per-month.
Option 2: A physical SIM bought in Japan
This is where the biggest surprise in this comparison sits. Buying a SIM at the airport and buying the same kind of SIM in town are not slightly different prices. They are 2.5x apart.
| Where you buy it | Plan | Price | In HKD |
|---|---|---|---|
| SoftBank counter, Narita T1 / T2 | 3GB / 5 days | ¥3,960 | HK$196 |
| AnyFone, Narita T1 / T2 | 4-day products from | ¥3,300 | HK$163 |
| IIJmio counter or convenience store | 3GB / 7 days | ¥1,600 | HK$79 |
| IIJmio | 5GB / 14 days | ¥2,400 | HK$119 |
| Sakura Mobile | 3GB / 30 days | ¥3,000 | HK$148 |
| Mobal | 5GB / 30 days | ¥4,500 | HK$223 |
An interesting detail: even the cheapest Japanese SIM here (IIJmio at HK$79) costs twice what a travel eSIM costs for the same trip. The airport counter costs nearly five times as much.
What you're paying for at the counter is immediacy and a person who speaks enough English to set it up. That's genuinely worth something if something goes wrong. It is not worth 2.5x.
And there are three costs nobody prints on the packaging:
- Your physical phone number goes offline. A tourist SIM is data-only in most cases. If you need a local number for restaurant bookings, that's a different product that often involves ID checks and a rental agreement.
- Your phone must be unlocked and on Japanese LTE bands (Band 1, 3 and 19 are the ones that matter). Confirm with your home carrier before you fly.
- You may have to configure APN by hand. It takes about five minutes and most people can do it, but it's five minutes standing in an arrivals hall rather than in your hotel.
There is one more thing worth saying plainly: several Japanese prepaid products require you to upload a photo of your passport and complete web registration, and SoftBank states processing can take up to 30 minutes. This is normal, it isn't a red flag, but it is not instant either.
Option 3: A travel eSIM
Install it before you leave, turn it on when you land, and you're connected in the time it takes the plane to taxi to the gate. Nothing to buy at the airport, nothing to swap, no passport photo.
For Japan, five days, these are today's prices:
| Plan | 5-day price | What you actually get |
|---|---|---|
| 1GB per day | HK$40 | 1GB of high-speed data each day, then unlimited at 256kbps until midnight UTC+8 |
| 2GB per day | HK$54 | 2GB high-speed each day, same rule after |
| 5GB per day | HK$73 | 5GB high-speed each day — most people will never touch the limit |
| Unlimited per day | HK$87 | No daily cap on high-speed data — the top tier, priced for heavy video use |
| 7 days, 1GB total | HK$12 | Cheapest option in the entire store, for light users |
It runs on KDDI and SoftBank locally — the same networks those airport SIMs rent. It is data-only and has no phone number attached.
See current Japan plans · Japan + Korea · all destinations
On that 256kbps floor (which applies to the metered 1GB, 2GB and 5GB tiers once you use them up): it is slower than the 512kbps most Hong Kong roaming plans drop to, and slower than China Mobile's 384kbps. This matters only if you plan to work from the connection. Maps, messaging, rideshare apps, email and translation all run fine. Video calls do not.
And one thing specific to Japan that almost nobody mentions: iPhones purchased in mainland China, Hong Kong or Macao cannot install any travel eSIM at all, including ours. If that's your phone, this whole option is unavailable to you and you should buy roaming or a physical SIM. Check your device before ordering.
When you should not buy a travel eSIM
Most articles comparing these three are written by someone selling one of them, so this section is usually missing. Four situations where a travel eSIM is the wrong answer:
- You need SMS verification codes. Banking, government services, some payment apps — these send codes to your own number. A travel eSIM does not carry it. If you'll need one even once during the trip, keep roaming available (see the setup below).
- You need a Japanese phone number. Not for restaurants — those use apps now — but for local deliveries, some hotel and clinic systems, and anything else that requires dialling you.
- Your phone is locked, or bought in mainland China / Hong Kong / Macao. Older carrier-locked phones can't use another operator's SIM; region-specific iPhones can't install travel eSIMs at all.
- You're going to mainland China and expecting the eSIM to solve the firewall. It won't. Whether you use roaming, a local SIM or our eSIM, you're on a mainland network and Western services stay unreachable without a VPN. I wrote that up separately — it's the single most misunderstood thing about travelling connected there.
The setup most travellers should actually use
You don't have to pick one. If your phone takes both a physical SIM and an eSIM — every iPhone sold outside mainland China does — use two:
So which one is yours
| If this is you | Buy | Why |
|---|---|---|
| I need my number reachable the whole time — work trip, expecting a code, travelling with family | Roaming package | HK$126 for five days from mainland China, HK$188 for 7GB/30 days on CMHK. It's the only category where nothing about your phone changes. |
| I don't need my number, and I care about price | Travel eSIM | HK$40 for five days. Nothing else in this comparison is close, and you can install it tonight instead of queueing at Narita. |
| I'm staying two weeks or more | Travel eSIM or long-validity local SIM | Daily plans are priced for short trips. Compare against a 15GB or 20GB total plan instead — see daily vs total-data plans. |
| I'm landing late, nothing's open, my phone needs to work now | Vending machine SIM at the airport, or roaming | The GPA machines at Narita run 24 hours. You'll pay more than you would in town; that's the price of 3am. |
| I genuinely don't know how much data I need | — | Work it out first — how much data a week actually takes. Guessing is how people end up either overpaying or throttled on day two. |
Quick answers
Is roaming really that much worse value? Depends entirely on whether you buy the package. On the daily rate, yes — CMHK's Freedom Zone at HK$68/day reaches HK$340 over five days, the worst line here. With the multi-day package it's HK$126 and perfectly reasonable. The gap between the two is 2.7x inside the same product.
Does an eSIM work if my phone is dual-SIM? Yes, and that's the recommended setup above. One line carries data, the other stays reachable.
Why is the airport SIM so expensive? You're paying for the counter, the staff and the fact that you're standing there jet-lagged with no alternative. The same networks, sold from a convenience store in the city, cost half to a fifth as much.
Will my travel eSIM work in mainland China too? Not if it's a Japan plan. Mainland coverage requires a plan that includes it, and it comes with its own rules about real-name registration and network access — see the FAQ.
Do I need to register my ID? For Japan, no. If your plan covers Hong Kong, yes — that's a Hong Kong rule, not a Japan one, and it applies whether you're using roaming, a local SIM or an eSIM. Macao and mainland China don't require it.
Prices verified 23 October 2026 from each provider's published rates; our own figures from live store pricing on the same date. Ours are listed like the others are — check current prices before you rely on any number here.