On Yay! it is currently possible to have multiple accounts.
However, we kindly ask for your understanding that you may experience limitations on how you can use your account if you create more than a certain number of accounts, as you will be considered to be advertising or spamming.
■Steps (For iOS and Android)
1. Save the account you are currently using and log out
2. You will return to the startup screen for Yay! so create a new account
・How to save an account
Also, regarding how to change accounts, you can easily change your account by long-pressing your account's icon at the bottom left of the screen.