When Michel heard what Niki said she was slackjawed at the sudden request. After a moment of stunned silence, Michel spoke, "if your parents are alright with it, then I suppose I can teach you." Niki nodded her head in response and took out her phone. She immediately called her parents and started explaining what had happened, as well as her decision to learn how to become a merc, so that she could get strong enough to defend herself.
Niki's parents were aware of the current situation of the current world. They were also aware that they could not say that they could protect their children in this kind of world. So Niki learning how to defend herself is a good thing. So after talking for a bit the two agreed and allowed Niki to learn from Michel.
Niki then handed her phone to Michel, who then started talking to her parents. After a short talk, the two sides came into an agreement.