That's no assassin that's a bard that delved in too deep in rogue levels, forgot he was a bard, and now that he doesn't kill people, his subconscious that retained all his bard energy is taking control
The only thing that bugs me about him is his lack of some common sense(I guess). Him being a extraordinary assassin, you'd think he'd know more about social interactions and about his society in general but he doesn't which makes some of the shit he says to others sound strange. What I'm getting from the manga is since his skills are really good, he doesn't have any need to learn to about blending into society which he is having slight problems with.
@Tsolux well he probably rarely made social interactions and gained info through spying and as we just saw... he is hot, apparently charismatic, and pretty good at fucking... sooo im pretty sure common sense isnt very high on his skill set