I like Chika and would love to help her but she and the mc can have sex before you see her leaving a client, so they are involved, or can be. Even after the mc asks her not to do it anymore she still does. So could ...kinda be ntr but they aren't romantic yet so I can be ok with it.
As you said, they had CASUAL sex, big difference, there was nothing romantic about it. Also you are barely starting to know each other, she has no obligation to comply to your request.
So what? You are just a stranger to her. You are keeping her to yourself when she is not even your girlfriend? LI is still a LI, if you don't like her, be a normal friend and stay away from her, no one force her to be your girl friend.
