(...) Raki is obviously nothing more than an author's tool. The manga needed a male presence, and somebody weak to make the Claymores seem stronger by comparison, and he had to be rather clueless so that Clare could explain things to him so that the readers would learn of it as well (it would be silly for Clare to talk to herself). I'm sure that any 'relationship' between them was originally only meant to be on some sort of child-mother level, to mirror the relationship that Clare used to have with Teresa, and to trigger changes in her character.
If you think of him as just that, he was actually a pretty well-executed storytelling device, ... but alas! Having him weak and clueless only served to get practically all Claymore readers to hate him (for being just useless as a character -- as opposed to a storytelling device).
And after that, he just got screwed up, when their relation suddenly (without explanation or indication) changed into some sort of... affection? or even love? Anyway, "the kiss" completely ruined it, and to me seemed like nothing but a (probably editor-enforced) attempt to include some romantic subplot in the story, to keep it popular, and to give Clare something of a "goal", (apart from just getting stronger to kill Priscilla).
Nothing was shown that could explain Clare's illogical 'obsession' with Raki, or her reason for not giving up on chasing after him for seven years. She's got more important things to do anyway. (...)