Fiore is a yandere to Mamoru Chiba, from Sailor Moon R: The Movie.
When he was a child, he was found by and taken care of by Mamoru Chiba. Mamoru was his only friend and the only human he thought was decent. Before he left, Mamoru gave him a rose as a token of their friendship (it was later revealed that Usagi was the one who gave him the rose). When he returns to Earth, he searches for Mamoru to show him the flower that he found especially for him.
Fiore is obsessed with Mamoru. He has held dear feelings for him since Mamoru was kind to him during his time on Earth. He also has a very low opinion of humans, believing all of them, except for Mamoru, are evil and selfish. Because of his onesided view on humans, he believes that he is the only one that Mamoru needs. He tries to kill Usagi because he views her as a rival for Mamoru.