For some reason she reminded me of Clover. Clover doesn't really fight that sixually like Onatopp does, but her dialog suggests that despite being a slave she enjoys killing people for her master. Also she's kind of an evil brainwashed prosttute who's always complaining of boredom when not fighting and killing people.
Do you think it's possible Clover gets some kind of weird twisted pleasure out of killing for her master like Onatopp does? It seems very possible to me. I think I'll roleplay as an evil badguy and Clover can be like Miss Onatopp for my character.