Updated: 2025-11-13 17:20:26
If you’ve already read the basic guide “eSIM Japan Guide: 10 Common Questions for First-Time Users” but still have questions about data validity, usage limits, setup methods, or whether you can keep your original SIM card, this article is made for you. In this advanced guide, we’ll dive deeper into the most common eSIM issues travelers face — and the ones that often cause confusion. All 10 Q&As below are based on real customer service cases, offering practical, experience-based advice. Especially the final question (installed but no internet connection), which is one of the most common inquiries we receive daily. We’ll show you the complete troubleshooting process — make sure to read until the end!
*If you’re still new to eSIMs and not sure where to start, check out this article first: “eSIM Japan Guide: 10 Common Questions for First-Time Users.” It explains everything clearly — from speed and cost to setup and plan selection — and will help you get started quickly.
Yes. The eSIM validity period is counted continuously from the activation date. As long as you bought a 16-day plan, you can fully use it during your 14-day trip without any issues.
Many travelers misunderstand the “High-Speed Data (HSD)” label on fixed-data eSIM plans, thinking it means a daily data allocation (e.g., 2GB or 3GB per day). They assume that if they stay in Japan for only 6 days, they can use only 6 days’ worth of data. That’s not how it works.
Using CDJapan Rental’s eSIM as an example: for fixed-data eSIM plans, “High-Speed Data” refers to the total data amount included in your plan — such as 30GB — and it is not divided by day.
This logic applies to all fixed-data eSIM plans, not just the 30GB/8-day one: the amount you purchase equals the total high-speed data you get, simply with a fixed period of validity.
For most Japan-only eSIMs, the period during which you can hold the purchase before activation is about 90 days, though many providers don’t clearly state this on their websites.
If you plan to buy early due to discounts or other reasons, we recommend checking with the seller first to confirm how long you can wait before activation.
Our general advice:
Almost all Japan travel eSIMs are designed for use within Japan only. They will not connect in other countries, and cross-border roaming is not supported.
If you need an eSIM that works across multiple countries, consider purchasing a “Global” or “Asia Regional” eSIM instead.
Many travelers purchase multiple eSIMs in a single order, but each QR code is issued per eSIM — not per item quantity in the same order. Therefore:
If you accidentally ordered multiple eSIMs together, the system will only generate one QR code.
Some providers have scheduled maintenance times. For example, CDJapan Rental performs system maintenance every Tuesday night to Wednesday morning (Japan Time). During this period, QR code generation may be delayed.
If your QR code appears blank or hasn’t been generated yet, please refresh the page after some time. If you purchased between Tuesday night and early Wednesday morning, it may only appear after around 9:00 AM Wednesday.
Usually, you don’t need to remove it. Most phones can hold both a physical SIM and an eSIM, but make sure that:
eSIMs are digital — no physical card is shipped. Everything is completed online, which is very convenient.
It’s recommended to switch your phone’s “mobile data” source to the eSIM. In most cases, you can keep your original SIM installed, but please pay attention to the following:
You don’t need to remove your original SIM — just make sure your phone is using the correct data source.
This depends on the provider:
For CDJapan Rental:
This is the most common and confusing eSIM issue for travelers. Most “installed but no internet” situations are caused by one of the following reasons.
If your phone shows the eSIM is installed, mobile data is on, and airplane mode is off — but you still have no connection — check the following one by one:
Many users have multiple profiles on their phones:
Your phone may automatically switch to another SIM, causing “no internet” issues.
Please confirm:
If you’ve used SIMs or eSIMs from other countries before, your phone might still retain old APN settings.
However, an eSIM only works with its own APN. If APNs overlap, the eSIM may fail to connect.
→ Delete all other APNs and keep only the one that came with your eSIM.
Most Japan eSIMs are for domestic use only (such as CDJapan Rental’s eSIM) and are not roaming eSIMs.
If your phone’s roaming remains on, it might connect to your original SIM’s roaming network — making it look like “no internet.”
→ Turn off international roaming.
After installing an eSIM, your phone may need a full restart to detect and apply new network settings.
If you’ve checked all four steps and still can’t connect, it’s likely that:
In that case, contact the eSIM provider’s customer service and share your order number along with a screenshot of the error. They can usually help resolve the issue quickly.
If you purchased your eSIM from CDJapan Rental, please contact customer support here: CDJapan Rental Customer Service or email rental@cdjapan.co.jp.
Please provide the following details:
With this information, the support team can quickly identify whether the issue is with settings or the local network signal.
While Japan eSIMs are fast and convenient — and don’t require any physical card delivery — the setup process can include small details that are easy to overlook. By carefully following these 10 advanced Q&As, you can likely resolve most issues, including the most common one: “Installed but no internet.”
We hope this guide helps you stay connected smoothly during your trip to Japan!
CDJapan Rental offers Japan-based eSIM plans with clear pricing, no hidden fees, and English-speaking support. Whether you’re traveling for business in Tokyo or sightseeing in Kyoto, you can pre-order before departure and get connected instantly upon arrival in Japan.
Want to explore available plans? Check out CDJapan Rental’s Japan eSIM Plans.
