From what we’ve gathered, Joules seem to be the purest essence of Anèria—the land of the Kaiju. They hold latent energy, ready to be released, but for too long concealed by stagnation.
When you collect a Joule, you hold a key to reanimating Anèria and saving it from the looming darkness.
A word to the wise, though: When you come into contact with a Joule, things… change. You might be referred to as a “Kaijin” or a “mysterious person.”