Thanks for the question. Unfortunately, you cannot access a single login from multiple devices using the LINE app. If you try accessing LINE from another device, the app on the previous device will be automatically deleted. You can access the same account from multiple devices using the LINE lite app. This app is available only for Android devices. But in your case, iPad being an iOS device, you cannot access the same account. I will keep an eye if they make a lite version for iOS devices. But for now, you can install the LINE app (Or one login) only on a single iOS device.