Kousaka Ruiza

A great magician and phantom thief.
He heard the protagonist holds the greatest gem in the world so he appears to steal it.
Ignoring the protagonist's pleas that she doesn't have the stone he forcibly stays close to her in order to find a chance to obtain it.

An arrogant guy who easily makes assumptions about things and only thinks in ways that are convenient for him, but somehow you just can't hate him.