I really don't quite understand why you'd want super obvious surnames like "love" and "keyheart". Go with something completely off the wall. Like Polish!
EX: Sora Czeberowski
No...? Okay, I'll go with German since it's a little easier to pronounce.
Sora Hellmann (ironically, despite the 'Hell' in the name, it means 'light man' )
Riku Unruh ( an agitator )
Kairi Schatz (treasure)
Meh, best I could come up with, as lame as it is. : P