Worried About Installing Your eSIM Wrong? It’s Easier Than You Think

“I'm always messing up my phone settings—what if I install the eSIM wrong?”
“I'm not tech-savvy. Just hearing the words ‘scan a QR code’ makes me a bit nervous…”

Don’t worry—these thoughts are completely normal. But the good news is: installing an eSIM isn’t as hard as you think. If you know how to scan a QR code, you’re already halfway there ✅
And honestly, the things people mess up are just a few common mistakes. As long as you follow the steps, you can avoid the headaches.

Common eSIM Installation Mistakes (and How to Avoid Them)

Mistake #1: Scanning the QR Code Before Arriving in Japan

Some people get too excited and scan their QR code right after receiving it—even before their trip begins. But for most eSIMs, the validity period starts from the moment you activate it.

If you’re using a Japan-based eSIM like the ones from CDJapan Rental, be sure to wait until you arrive in Japan before scanning the code. That way, you won’t waste your data period.

Pro Tip: Print out the eSIM instructions or save them on your phone before you leave. When you land in Japan, just follow the steps one by one.

Mistake #2: Forgetting to Enable Data Roaming After Scanning

Some users assume “data roaming” means high charges, so they avoid turning it on.

But that’s not quite right. If you’ve installed an eSIM and your original physical SIM doesn’t have mobile data turned on, you won’t incur roaming charges.

Turning on data roaming is necessary for the eSIM to connect properly—especially for international eSIM brands like Ubigi or Airalo.

However, if you’re using a Japan-local eSIM from a domestic provider—like CDJapan Rental, which uses docomo’s network—then you don’t need to enable data roaming. Just start using your eSIM normally in Japan. Local eSIMs connect directly to domestic networks, making setup easier and signals more stable than those using international carriers that piggyback on Japanese networks.

Mistake #3: Not Selecting the Correct Mobile Data Line

After installing your eSIM, don’t forget to go into your settings and check which line is set as your mobile data source.

On iPhones, go to Settings → Cellular, and make sure your newly installed eSIM is selected as your default data line. If you still have your physical SIM inserted, your phone may automatically switch back to it, so it’s best to turn off your physical SIM to avoid any confusion.

Worried About Making a Mistake? Here’s How to Stay Safe

Still feeling a little nervous? These tips might help:

• Save or print your QR code before you leave so you’re not scrambling to find it last-minute
• Use free Wi-Fi at the airport in Japan to complete setup more smoothly
• Watch a tutorial video or go through the step-by-step screenshots before trying it
• CDJapan Rental also provides easy-to-follow setup guides in English
• If you’re still unsure, you can contact customer service (it’s not 24/7, but they usually respond quickly)

Final Thought: You Don’t Need to Be a Tech Geek—Just Follow the Steps

You really don’t need any advanced tech skills. If you can use LINE and know how to scan a QR code, you’re totally capable of installing an eSIM.

You might feel nervous the first time, but once you’ve done it successfully, you’ll think, “That was way easier than I expected” 😉