This is pretty much what they're like according to my headcanon: First they fight mercilessly, killing each other over and over again, until, at long last, one of them grows so exhausted from the fight that they finally lose consciousness... and only then does the one left standing allow their stubborn pride to melt away, only then does the one left standing allow themselves to be honest with how they really feel, only then do they exchange tender affection with their bitter and beloved rival... Either way, it's still passion. It just assumes different shapes. Just like a flickering flame, or a moon going through its phases.