Assassin & Cinderella 01 (manga)

Neneko is a spy blessed with catlike charms. Her mission? Seduce the ace assassin of a rival organization and expose his weaknesses. The problem? She's blown her cover before learning a thing! But rather than dispose of her, the target makes an indecent proposal: marry him and take their relationship to the next level, since he can't keep his hands off her body! Is his clinginess an act, or could there be genuine love behind his murderous gaze?!