1. What you need before starting

Before installing IIJmio eSIM, prepare these:

Item	Why you need it
Wi-Fi connection	eSIM profile cannot be downloaded without internet. IIJmio also says the device must be connected to Wi-Fi before setting up the eSIM profile. (iijmio.jp)
SIM-free / unlocked phone	IIJmio notes that SIM-locked devices cannot install the eSIM profile. (iijmio.jp)
eSIM-compatible iPhone or Android	The phone must support eSIM.
IIJmio activation code / QR code	Used to download the eSIM profile.
mioID and password	Needed for the My IIJmio app and account management.
Another device, if using QR code	Easiest method: show QR code on laptop/another phone, scan it with the phone that will use IIJmio.

Important: Do not delete the eSIM after installing it. IIJmio says the activation code can only be set once on a device and cannot be reused on another device. (iijmio.jp)

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2. Apps and tools you need

Main app: My IIJmio

Install My IIJmio from:

• App Store for iPhone
• Google Play for Android
• HUAWEI AppGallery for Huawei devices

IIJmio says My IIJmio is the official app for checking remaining data, buying extra data, checking contract details, and changing settings. It also supports high-speed data ON/OFF. (help.iijmio.jp)

You will use My IIJmio mainly for:

• Downloading the APN configuration profile on iPhone
• Checking remaining data
• Checking contract/service status
• Turning high-speed data ON/OFF
• Buying extra data
• Checking plan and billing details

Apps/tools used during setup

App / Tool	iPhone	Android	Purpose
Settings app	Yes	Yes	Add eSIM, select data line, configure network
Camera app	Yes	Yes	Scan eSIM QR code
My IIJmio app	Yes	Recommended	APN profile download, data usage, contract check
Safari / Chrome	Yes	Yes	Open IIJmio activation page or account page
App Store / Google Play	Yes	Yes	Install My IIJmio

Do not use the old IIJmio Coupon Switch / mioPON app. IIJmio ended that app on September 30, 2024 and says users should use My IIJmio instead. (iijmio.jp)

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3. IIJmio APN settings

For Android manual APN setup, use these values:

Field	Value
Name	iijmio or IIJmio
APN	iijmio.jp
Username	mio@iij
Password	iij
Authentication type	PAP or CHAP

IIJmio’s English setup page lists these exact APN values. (iijmio.jp)

Leave other fields blank/default unless your phone requires them.

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4. iPhone setup guide

Step 1: Connect to Wi-Fi

Go to:

Settings → Wi-Fi → ON

Connect to a stable Wi-Fi network.

You need Wi-Fi because the eSIM profile must be downloaded from IIJmio.

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Step 2: Add the IIJmio eSIM

Go to:

Settings → Cellular / Mobile Service → Add eSIM

Then choose one of these methods:

Method A: Scan QR code

Choose:

Use QR Code

Scan the IIJmio eSIM QR code from another phone, laptop, tablet, or printed paper.

Apple’s iPhone eSIM setup supports QR-code activation through Settings → Cellular → Set Up Cellular / Add eSIM → Use QR Code. (Apple Support)

Method B: Enter activation code manually

Use this if QR scanning does not work.

Go to:

Settings → Cellular / Mobile Service → Add eSIM → Use QR Code → Enter Details Manually

Enter:

• SM-DP+ Address
• Activation Code

IIJmio’s support page also describes manual eSIM activation using the SM-DP+ address and activation code. (help.iijmio.jp)

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Step 3: Label the eSIM

After adding the eSIM, iPhone may ask you to label it.

Recommended label:

IIJmio

If you have another SIM already, label the other one as:

Main, Primary, or your home carrier name.

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Step 4: Select IIJmio for mobile data

Go to:

Settings → Cellular / Mobile Service → Cellular Data

Select:

IIJmio

If you use two SIMs, turn Allow Cellular Data Switching OFF while testing. This avoids confusion about which SIM is providing data.

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Step 5: Configure IIJmio line settings

Go to:

Settings → Cellular / Mobile Service → IIJmio

Check these:

Setting	Recommended value
Turn On This Line	ON
Cellular Data	ON
Voice & Data	LTE / 4G first
Data Roaming	ON for testing
Network Selection	Automatic

For the first test, choose LTE / 4G, not 5G. Once 4G works, you can try 5G later if your plan and phone support it.

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Step 6: Install IIJmio APN profile on iPhone

This was the step that fixed your phone.

Open My IIJmio app.

Choose:

APN構成プロファイルダウンロード
That means Download APN Configuration Profile.

Then allow the download.

After downloading, go to:

Settings → General → VPN & Device Management

Tap the downloaded IIJmio APN profile and install it.

For iOS 15 and later, IIJmio’s official instruction is:

Settings → General → VPN & Device Management → install downloaded APN profile. (iijmio.jp)

For iOS 14, IIJmio says the path is:

Settings → General → Profile → install downloaded APN profile. (iijmio.jp)

Apple also notes that after downloading a configuration profile, you must go into Settings and install it; downloading alone is not enough. (Apple Support)

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Step 7: Restart and test

Restart iPhone.

Then:

1. Turn Wi-Fi OFF
2. Make sure Cellular Data = IIJmio
3. Open Safari
4. Try any website
5. Check for 4G / LTE / 5G

If internet works, setup is complete.

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5. Android setup guide

Android menus vary by brand, but the flow is similar.

Step 1: Connect to Wi-Fi

Go to:

Settings → Wi-Fi → ON

Connect to Wi-Fi before installing eSIM.

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Step 2: Add eSIM

Google Pixel style path

Go to:

Settings → Network & Internet → SIMs → Add SIM / Download a SIM instead

Then scan the IIJmio QR code.

Samsung Galaxy style path

Go to:

Settings → Connections → SIM manager → Add eSIM

Then scan the IIJmio QR code.

Other Android phones

Look for one of these:

• SIMs
• Mobile Network
• SIM Manager
• Download eSIM
• Add eSIM
• Add mobile plan

Scan the IIJmio QR code.

If QR code does not work, choose manual entry and enter:

• SM-DP+ Address
• Activation Code

IIJmio’s support page gives Android manual-entry guidance using the Android network/SIM menu. (help.iijmio.jp)

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Step 3: Select IIJmio as mobile data SIM

Go to:

Settings → Network & Internet / Connections → SIMs / SIM Manager

Set:

Setting	Value
Mobile Data	IIJmio
Calls	Your choice, if voice plan
SMS	Your choice, if SMS/voice plan

If using two SIMs, select IIJmio specifically for mobile data.

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Step 4: Configure APN on Android

Go to one of these paths:

Pixel / stock Android

Settings → Network & Internet → SIMs → IIJmio → Access Point Names

Samsung

Settings → Connections → Mobile Networks → Access Point Names

OPPO / Xiaomi / Motorola / others

Usually:

Settings → SIM card & mobile network → IIJmio → Access Point Names

Then tap:

+ or Add

Enter:

Field	Value
Name	IIJmio
APN	iijmio.jp
Username	mio@iij
Password	iij
Authentication type	PAP or CHAP

Then tap:

Save

Return to the APN list and select the new IIJmio APN.

IIJmio’s Android guidance says to open Access Point Names, create a new APN, save it, return to the APN list, and select the created APN. (iijmio.jp)

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Step 5: Restart and test Android

Restart the phone.

Then:

1. Turn Wi-Fi OFF
2. Turn Mobile Data ON
3. Select IIJmio as data SIM
4. Open Chrome
5. Test internet
6. Confirm 4G / LTE / 5G appears

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6. 5G notes for IIJmio

Do not panic if you only see 4G / LTE.

IIJmio says Type D SMS SIM and data eSIM on docomo network cannot use 5G. It also says some Type D and Type A voice/data combinations can use 5G if the device supports it. (help.iijmio.jp)

So:

• 4G/LTE working = setup is successful
• 5G missing does not always mean a problem
• First make 4G/LTE stable, then check 5G later

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7. Troubleshooting checklist

Problem: Signal bars show, but no 4G/LTE and no internet

Most likely causes:

• APN profile missing on iPhone
• Wrong APN selected on Android
• Another carrier APN/profile installed
• IIJmio not selected as cellular data SIM
• eSIM line is installed but turned off

Fix:

iPhone

Check:

Settings → General → VPN & Device Management

If you see an old carrier profile, remove it.

Then install IIJmio APN profile from My IIJmio → APN構成プロファイルダウンロード.

Android

Check:

Settings → Mobile Network → Access Point Names

Make sure APN is:

iijmio.jp

Username:

mio@iij

Password:

iij

Authentication:

PAP or CHAP

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Problem: “Profile Downloaded” does not appear on iPhone

This means the profile was not downloaded or was already installed.

Check:

Settings → General → VPN & Device Management

If IIJmio profile is already there, it is installed.

If no IIJmio profile appears, download it again from My IIJmio.

Apple says only one profile can be ready to install at a time; if you download another profile before installing the first one, only the second one remains available. (Apple Support)

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Problem: Internet still does not work after APN setup

Try in this order:

1. Turn Airplane Mode ON for 30 seconds, then OFF
2. Restart phone
3. Confirm IIJmio is selected for mobile data
4. Set network mode to LTE / 4G
5. Turn Data Roaming ON temporarily
6. Reset network settings

iPhone reset path

Settings → General → Transfer or Reset iPhone → Reset → Reset Network Settings

Android reset path

Usually:

Settings → System → Reset options → Reset mobile network settings

Menu name depends on the Android brand.

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Problem: QR code already used or eSIM deleted

This is the annoying one. IIJmio says the activation code can only be configured once and cannot be reused on another device. (iijmio.jp)

So do not delete the eSIM unless IIJmio support tells you to. If deleted, you may need eSIM reissue from IIJmio.

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8. Quick setup summary

iPhone short version

1. Connect to Wi-Fi
2. Settings → Cellular → Add eSIM
3. Scan IIJmio QR code
4. Select IIJmio for cellular data
5. Install My IIJmio
6. Download APN profile from APN構成プロファイルダウンロード
7. Install from Settings → General → VPN & Device Management
8. Restart iPhone
9. Turn Wi-Fi off and test mobile data

Android short version

1. Connect to Wi-Fi
2. Settings → Network/SIM → Add eSIM
3. Scan IIJmio QR code
4. Select IIJmio for mobile data
5. Add/select APN:
   • APN: iijmio.jp
   • Username: mio@iij
   • Password: iij
   • Authentication: PAP or CHAP
6. Save APN
7. Restart Android
8. Turn Wi-Fi off and test mobile data

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Final practical advice: for iPhone, installing the IIJmio APN profile is the key step when signal appears but mobile data does not work — exactly what happened in your case.