If you forgot your registered password, there is no way to check it. Please change your password on the smartphone version of LINE.
Note: After setting your new password, be sure to keep it safe so you don't forget it.
1. Start the smartphone version of LINE.
2. Tap the Home tab > Settings > Account.
3. Tap Password.
4. Enter a new password, then tap Change password.
Note: In some cases, you may need to enter your smartphone's unlock method.
If you're trying to transfer your account and don’t have access to your old device, see this Help article
Let us know if we can make it better.