Only play multiple accounts on a device if they’re all attached to Supercell IDs. Below are instructions for creating Supercell IDs for your villages and for switching between them. If you haven’t attached the current active village to a Supercell ID:
When you have at least one account attached to Supercell ID and want to create a Supercell ID for your second account:
Repeat these steps for each of the other game accounts you have been playing on your device. To switch between your Supercell IDs, logout from Supercell ID in Settings and select "Play with Supercell ID" in the title screen. You will be presented with a menu of all your saved Supercell IDs. Play smart!