It is possible to battle other users by creating a room from the 「Private Matches」 located at the right side of the home page at the social screen.
It is possible to set battle settings upon creation (Play with cards and Towers at their current Lv./Play with cards and Towers at Lv. 9)
A passcode will be issued and you can share it with an opponent. You may need to wait awhile after pressing the FIGHT button.
It is possible to share the passcode through SNS like LINE by tapping on the Share button beside the passcode.