The Ultra Beasts in Pokemon Sun and Moon are Personas. Let me tell you why.
They are considered to be legendaries, yet they come in various numbers. Though, they are limited. Each of them are very unique in their own way. Like a persona. Finally, here is the shocker! THEY ARE BEASTS AND PERSONAS ARE BEASTS TOO. ADD IN AN ULTRA BEAST IN PERSONA 5, YOU WOULDN'T THINK NO DIFFERENT. DEADASS SERIOUS!