Is no one going to mention that one part of the tl that does not make any sense??
How in the world does that make any sense, especially in that context?
So, I went to look for the raw and found out that the boy was actually saying,
Sayu is underage, and she doesn't go to highschool where it should have been mandatory, and she's living with a non family ossan. It wouldn't be weird if she called the police.