Board Thread:News and Events/@comment-26005122-20160601070850/@comment-26005122-20160602233932

So, from what I found out, anybody using a child account, won't have access to the Part II event. A child account is created when you enter your age under 18 on a brand new game. This account won't give you the option to tie a LINE account to the game. Your name will appear as Player on the score rankings screen.

Unfortunately, there's no way to turn a child account into an adult guest account, or tie it to a LINE account without losing your game progress.