nagisa is a happy, energetic boy, excited for his soulmate.
rei is more stiff than him and doesn't actually believe in the soulmates thing. but they have the same date on their wrists, implying they're soulmates.
nagisa is desperate for love from his soulmate, hoping to god that everything will work out when they meet.
rei, on the other hand, could not care less about a relationship, he just wants to be proven right.