Follow these instructions to check which account is currently linked in the app.
1. From the Menu on the title screen or the Misc. menu within the game, select Account Management.
2. Check the e-mail address displayed under Registered e-mail address.
・ Tapping Manage Account Info will open up the Nintendo Account Account Management screen.
・ Please check the e-mail address registered to your Nintendo Account by tapping User Info in the Nintendo Account Account Management screen.
・ The Nintendo Account that is displayed on the Nintendo Account Account Management screen is the one you are logged in on in your browser, so it is possible that it will display a different Nintendo Account from the one to which you have linked your save data.