Black Survival can be signed in with Google or Apple ID.
Therefore, if you have multiple Google or Apple ID, you can use multiple accounts on a single device.
On your device, go to 'Settings - Account - Add Account' and create new Google account.
Open Black Survival, in main lobby, go to 'Settings - Sync Device - Connected to Google'
Pop up will appear with list of added accounts to your device.
Select the account you would like to sign in with on the list.
Go to https://appleid.apple.com/account#!&page= and create new Apple ID. Next, go to Game Center, sign in with Apple ID, and open Black Survival
You can make a new account by making a new Steam account