There are times when you may notice your team leader on fire. Maybe you took a hit while trying to lay on some heavy damage, or you had to dash to avoid said hit. What's that flame all about? Does it hurt me?
The flame around your party leader indicates that you can re-form your last Unite Morph. Let me explain:
All Unite Morphs have a certain duration, with larger Morphs lasting shorter than smaller ones. If it's forced to disassemble (for example, if an enemy blocks your attack and breaks it, or if you perform a dash) before it expires, however, you have a chance to renew it, indicated by a flaming aura around your team leader. As long as you have enough conscious party members, you can re-form the same Morph without having to draw a new Wonder-liner. Don't forget, though, that a Morph's time can still run down and expire even when you're not using it; watch for the flame to flash, as this indicates that the Morph is about to expire.