Before you begin to set up RealVPN IKEv2 connection on your Android device, you need to get your VPN account credentials from the RealVPN's User Settings.
Sign in with your account at https://realvpn.io
Open the dropdown Account menu and click Settings.
In the opened window select the required VPN server you want to connect to.
Then select the IKEv2 protocol from the list.
Click Generate to get the connection data.
Now proceed to set up the connection on your Android device.
Now you have the RealVPN connection established.
Use the strongSwan VPN Client to enable\disable VPN connection.