You're brushing your mouth with a cross shaped thing. You're doing the action of this brushing over and over hoping to summon Jesus, who will help to solve the matter of your cavities.
You try the special action out. You brush in a cross pattern, and *poof* Jesus (じ) appears in your mirror, blessing you and your teeth. "Jesus, you're here!" you say through your toothpaste filled mouth.
Currently there are no similar looking kanji which exist in the WaniKani learning system