Maki Harukawa is the ultimate assassin. She has a very serious personality, and she doesn't really seem to smile much if at all. Despite her cute appearance, Maki is described as a hostile misanthrope of few words. She is very aware that she comes across as unfriendly and prefers to be alone. In general, she dislikes people and thus she is not very cooperative and can be stubborn. Just keep trying, I'm sure she'll open up more with time.