Unlike the other two Nurture actions, Petting is not a mini-game. It does not require any Energy or item in order to perform. Petting one's Genopet will directly boost Love. Once maximum Love has been reached, players can continue to pet their Genopet, but will receive no incremental benefits to Mood.
Petting can be accomplished by swiping on one's Genopet with 2 fingers.