In first season, a very smart boy named Urawa Ryo was doing as well as she did in school, which naturally intrigued her. They were interested in each other, and it turned out, not only was he smart, but he had pyschic powers, so he knew that she was Sailor Mercury (though she denied it up and down, he had seen her in a dream that forecasted that he would become a monster and attack her). So that happened and, Surprise! he was healed, so he went off to be good enough to challenge Ami intellectually without using his psychic ability.
Even though supposedly his pyschic ability was enhanced by the rainbow crystals (the pure heart/beautiful dream mirror/star seed of the season), he still retained enough of the ability to come back in a later ep knowing that his life was in danger. Incidently, he was willing to kill himself so that the villains couldn't use him for their own evil deeds. Heather thinks it's worth mentioning. Obviously, he's still living.
Anyway, he's the only guy Ami's shown an interest in ever, w/ the exception of the Starlights, but they left & are never coming back & nothing ever happened much there anyway. Ryo was a lot cuter. So he gets to be Ami's husband, and now he's a Knight for Mercury. His element of emotion must be either psychic ability or wisdom. I'll tell you when I know.
So anyway, that's where Ryo is coming from. It's mostly important that he's Ami's husband, a Knight, smart, and psychic. Especially, the latter.