AmiRyo

AmixRyo is a het ship between Ami Mizuno (aka Sailor Mercury) and Ryo Urawa in the Sailor Moon series.

Canon
Ryo Urawa possessed one of the Seven Great Youma, Bunbo, which gave him psychic powers. He used these powers to score well on tests. He admired Ami who had natural intelligence and had a crush on her.

Even after being transformed into a Yhouma Ryo was able to keep control of himself for a short time.

Like most anime-only characters in the first season he does not appear in the later seasons.

Fanon
It is a less fairly popular shipping.