Optus roaming in Japan is convenient, but it can get expensive fast. At up to 10 AUD per day, roaming charges can add more than 100 AUD to a two-week trip. Before you switch on roaming, it's worth understanding Optus' costs, daily data limits, and whether a local Japan eSIM could give you more data for less while letting you keep your Australian number active.
TL;DR: Optus roaming in Japan costs 5-10 AUD/day and caps you at 1 to 5 GB. Over 14 days, that adds up to 70-140 AUD. A 14-day trip on Sakura Mobile costs you ~60.60-80.79 AUD, with no roaming passes or daily resets to track. Sakura Mobile also lets you keep your Australian number active for calls and texts while your eSIM handles the data.
- Does Optus Roaming Work in Japan?
- How Much Does Optus Roaming Cost in Japan?
- Which Japanese Network Will You Connect To?
- How Optus Roaming Billing Actually Works
- How to Turn On Optus Roaming for Japan
- The Real Cost of an Optus Trip to Japan
- Optus Roaming vs. Sakura Mobile
- Which Sakura Mobile Plan Fits Your Trip?
- Keep Your Australian Number: Dual-SIM Setup with Sakura Mobile
- Optus in Japan FAQ
- One Last Thing Before You Fly to Japan
Does Optus Roaming Work in Japan?
Yes. Optus roaming works automatically in Japan once you land. It runs on Choice Plus, Standard Postpaid, and Prepaid plans, and connects you to a local partner network like SoftBank or NTT docomo. You don't need to pick a network by hand—your phone finds one on its own as soon as you arrive.
This makes Optus easy to use. But easy doesn't always mean cheap, especially if you're on Japan's data-heavy apps for two weeks straight—maps, translation tools, and photo uploads add up fast.
How Much Does Optus Roaming Cost in Japan?
Optus roaming in Japan costs 5 AUD/day on Choice Plus for 5 GB, or 10 AUD/day on Standard Postpaid for just 1 GB. Prepaid customers pay 5 to 35 AUD depending on the add-on. Skip a plan entirely, and you'll pay 1 AUD per MB—a rate that can turn one Google Maps session into a 20+ AUD surprise.
Optus Japan Roaming Plans Compared
| Plan | Daily cost | Daily data | Notes |
|---|---|---|---|
| Choice Plus | 5 AUD/day | 5 GB | Auto renews at 5 AUD for another 5 GB if you go over |
| Standard Postpaid | 10 AUD/day | 1 GB | Tightest daily cap of the three |
| Prepaid Flex Plus | 5 AUD/day or 35 AUD/7 days | 1 GB/day 7-day pool | Manual pack purchase required |
| Pay-As-You-Go | No plan | None | 1 AUD/MB—avoid this rate at all costs |
What Happens If You Go Over Your Daily Limit
If you use up your daily data, Optus either charges you again for another day of data or slows your speed down, depending on your plan. On Choice Plus, going over means an automatic 5 AUD charge for another 5 GB, so it's worth checking the My Optus app if you want to avoid surprise charges to your bill.
Which Japanese Network Will You Connect To?
Optus roaming in Japan uses partner networks such as SoftBank and NTT docomo. Coverage, speeds, and connection quality can vary depending on the available partner network, and Optus does not guarantee roaming coverage or performance overseas.
5G roaming is only available in selected countries and on compatible devices. Your phone must also support the local network and VoLTE roaming to access the best available service in Japan. Because roaming partners and network availability can change over time, it's a good idea to check your device's compatibility before you travel.
If you're looking for a more predictable connection, Sakura Mobile's 3GB/day and Unlimited eSIM plans connect directly to 5G networks in Japan, giving you local coverage from the moment you arrive.
How Optus Roaming Billing Actually Works
The 24-Hour Reset Rule
Your Optus data resets every 24 hours from the moment you first use it—not at midnight. Whatever you don't use during that window doesn't carry over, so a light-use day doesn't save you data for a heavier one later in the trip.
Auto Top-Up on Choice Plus
If you use all 5 GB on Choice Plus, Optus automatically charges you 5 AUD more for another 5 GB. This keeps you connected. But it also means a data-heavy day can quietly double your cost, with no extra step on your part. You can turn this off in the My Optus app if you'd rather hit a hard stop instead.
How to Turn On Optus Roaming for Japan
Turn on Optus roaming by checking your plan in the My Optus app, then switching on Data Roaming in your phone's settings before you land.
- Open the My Optus app and confirm your roaming plan is active.
- Go to your phone's Settings, then Cellular (iPhone) or Network & Internet (Android).
- Turn on Data Roaming.
- Land in Japan and your phone should connect within a few minutes.
If you don't see a signal after landing, toggle Airplane Mode on and off—this often forces your phone to search for a network again.
The Real Cost of an Optus Trip to Japan
A 14-day trip on Optus Standard Postpaid costs about 140 AUD, while the same trip on Choice Plus runs about 70 AUD. Sakura Mobile's 3GB/day eSIM plan costs about 60.60 AUD—cheaper than either Optus option, with direct connection to Japanese networks.
| Option | Daily cost | 14-day total | Data limit |
|---|---|---|---|
| Optus Standard Postpaid | 10 AUD/day | ~140 AUD | 1 GB/day |
| Optus Choice Plus | 5 AUD/day | ~70 AUD | 5 GB/day |
| Sakura Mobile 3 GB/day | — | ~60.60 AUD (6,930 yen) | 3 GB/day high-speed (then reduced speed) |
| Sakura Mobile Unlimited | — | ~80.79 AUD (9,240 yen) | No cap |
Note: Sakura Mobile's prices are listed in JPY and converted to AUD on August 31, 2026. Check current pricing before you book, as the exchange rates shift.
Compared with Optus' better-value Choice Plus tier, Sakura Mobile's Unlimited Plan costs slightly more, but you get unlimited data and don't have to track daily usage.
Optus Roaming vs. Sakura Mobile
| Details | Optus Roaming | Sakura Mobile eSIM |
|---|---|---|
| Data | Choice Plus: 5 GB/day Standard: 1 GB/day | 3GB/day plan: 3 GB (then slowed) Unlimited plan: no cap |
| Typical 14-Day Cost | Choice Plus: 70 AUD Standard: 140 AUD | 3GB/day: ~60.60 AUD (6,930 yen) Unlimited: ~80.80 AUD (9,240 yen) |
| Hotspot / Tethering | Included | Included |
| Calls & SMS Over Network | Included | Data-only (keep SIM active as secondary) |
| Keep Your Aussie Number | Yes (uses home SIM) | Yes (keep SIM active as secondary) |
| Setup | Automatic on first use | Scan QR code |
| Support | Phone | Online, phone, in-person (Shinjuku office, Kansai/Fukuoka Airports) |
| Network | Roaming partner | Direct (docomo/au) |
| Network Speed | 5G not guaranteed (depends on device and partner network) | 5G on both plans |
When Optus Choice Plus Is Still a Good Call
If you're taking a short trip and only need maps and messages, Optus Choice Plus is a fair, simple option. There's nothing to set up. It just works the moment you land, which is ideal if you'd rather skip an eSIM installation altogether.
Which Sakura Mobile Plan Fits Your Trip?
Unlimited vs. 3GB/Day High-Speed—How to Choose
Choose Unlimited if you stream vidoe, use social media heavily, or travel for a longer stretch. Choose the 3GB/day plan if you mainly use maps, messages, and photos, and you're comfortable with slower speeds if you go over.
| Traveler type | Trip length | Data habits | Best fit |
|---|---|---|---|
| Light user | 3-5 days | Maps, occasional messages | Optus Choice Plus |
| Content-heavy / remote work | 7-10 days | Streaming, hotspot, uploads | Sakura Mobile 3GB/day |
| Long-stay / high-data user | 10+ days | Streaming, social media, video calls, and daily browsing | Sakura Mobile Unlimited |
Keep Your Australian Number: Dual-SIM Setup with Sakura Mobile
Turning Off Optus Data Without Losing Calls or Texts
You can turn off Data Roaming on your Optus line and still get calls and texts, since those don't need a data connection. Your Optus SIM stays in your phone as normal—you're only switching off the data part, not the whole line.
Keep 2FA and Bank Codes Working
Your Optus number stays active for bank codes and two-factor logins as long as you keep the SIM in, and Data Roaming turned off. This is one of the main reasons travelers keep their Australian SIM in instead of swapping it out completely.
Set Up Your Sakura Mobile eSIM in 3 Steps
- Buy your Sakura Mobile eSIM plan online before your trip.
- Install and activate your eSIM over WiFi after you land in Japan.
- Connect to the internet by switching your mobile data to your Sakura Mobile eSIM while keeping your Optus SIM active for calls and texts.
Optus in Japan FAQ
- Q1: Does Optus roaming work in Japan?
Yes. Optus roaming works automatically in Japan on Choice Plus, Standard Postpaid, and Prepaid plans, connecting you to a partner network like SoftBank or NTT docomo as soon as you land.
- Q2: How much does Optus roaming cost in Japan per day?
Optus charges 5 AUD/day for Choice Plus (5 GB) or 10 AUD/day for Standard Postpaid (1 GB). Prepaid add-ons range from 5 to 35 AUD, and pay-as-you-go without a plan costs 1 AUD per MB.
- Q3: Does unused Optus data carry over to the next day?
No. Optus roaming data resets every 24 hours from your first use, and anything left unused at the end of that window is gone—it does not roll over to your next day.
- Q4: What happens if I go over my Optus daily data limit?
On Choice Plus, going over automatically charges you 5 AUD for another 5 GB. On other plans, you may be slowed down instead, so it's worth checking My Optus app to see how your specific plan handles overages.
- Q5: Can I use Optus and a Japan eSIM at the same time?
Yes. You can keep your Optus SIM active for calls, texts, and bank codes while turning it off for data roaming, then use a Sakura Mobile eSIM for your data. This dual-SIM setup is common for travelers who want to keep their Australian number reachable.
- Q6: Which network does Optus connect to in Japan?
Optus roams onto partner networks in Japan, like NTT docomo, SoftBank, and au. Optus doesn't guarantee coverage or quality on these partner networks, and 5G roaming is only available in selected countries, so your connection speed can vary depending on your device and location.
- Q7: Is Sakura Mobile's unlimited plan really unlimited?
Yes. The Unlimited plan has no high-speed data cap. The 3GB/day plan slows down once you pass your daily high-speed allowance, but won't cut you off from the internet completely.
FAQ
One Last Thing Before You Fly to Japan
If you're still deciding, the numbers are simple: even Sakura Mobile's Unlimited plan costs less over 14 days than the Optus Standard Postpaid, and you won't need to watch a daily counter for your whole trip.
