Cross-Dressing Villainess Cecilia Sylvie, Vol. 3 (light novel) — Hiroro Akizakura

What a pleasantly surprising twist -- never thought I, Dante, assassin extraordinaire, would see the day when a girl would try to strike a deal with me...but now I have! What's more, it's so fun to tease Cecilia-as-Cecil, 'cos the reactions of the good Prince Oscar and the duke's son are priceless. There's just one thing bothering me -- the assassin group I've been with since I was a kid is getting all worked up about how chummy I am with those three. I just hope none of our guys do something stupid like kidnap her...