Love accounts for the remaining 20% of Mood with a maximum score of 100. A Genopet with maximum Love will have 20% of their maximum possible Mood without taking other needs into account.
Petting is the player action which can increase Love. Love decays 50 points every 24 hours starting from the time of the last successful Petting action. When Love is 0, a Genopet's Mood is effectively capped at 80% of its possible maximum.