Riolu are known to see the emotions of others in the form of mysterious auras. But the emotions displayed by humans frequently differ from the true ones shown in the auras which Riolu see. For instance, a person in deep despair may wear a smile, lest another person try in vain to cheer them up and do nothing but strengthen their sorrows. Conversely, a person at a funeral may attempt to cry and suppress unrelated joys, lest it be thought they are happy about the deceased's parting.

Pokemon trainers in particular must learn to keep a steady face, for visible elation can convince an opponent to quickly change tactics, and visible disappointment can likewise give an opponent confidence. Most ignore their foe's faces, lest they be fooled by a deceptive expression, but wearing one's emotions on their sleeve is a quick way to lose a battle, and this is as true of pokemon as their trainers.

Riolu are young pokemon, still learning to attach the myriad of auras people and pokemon display to their emotions. In the wild, they seclude themselves in remote caves where few humans venture, for wild pokemon do not yet know how to lie about their emotions. If a domestic Lucario lays an egg, or a Riolu is captured before evolution, trainers must find somewhere equally remote and take care to display their emotions openly for the duration of their training. This is a difficult task to learn, and no less hard to unlearn, and the distance one must travel to find the right location is nearly as great a hardship. But if their trainer fails to train them where faces are honest, Riolu will never learn to use auras to see through their opponents' strategy and witness the true feelings behind a pokemon battle.