Sometimes it feels good to start fresh. To start an entirely new game, you first need to connect your current game to Supercell ID if you haven't already, so you don’t lose all that progress in case you ever want to return.
To connect, open the in-game Settings and tap ‘Connect’ under the Supercell ID heading. Follow the on-screen instructions.
After this you can start a new game:
Open the in-game Settings.
Open the Supercell ID Menu.
Tap the cogwheel to access the Supercell ID Settings.
Tap ‘Log out’ in the Supercell ID options.
Now, in the game's title screen, select ‘Play without Supercell ID’.
All done!
You should now create a Supercell ID for your new account. This will make switching between your two accounts very easy and will keep your accounts safe.