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.