It feels like the author is clueless to how dangerous this kind of situation would be for an actual middle schooler, and how irresponsible the message of "it's fine because I've known them for a while" is. Meeting up with strangers who's voice you've never even heard before is crazy for someone that young.
If they wanted to make it okay, they could have had it that Makoto was related to Ao, like grandad or granduncle, and only found out after the meeting. Then, like a responsible adult, had a talk with his parents, with the decision being that he could meet the other friends but with the supervision of his grandfather, Ao.
That way he gets properly scolded and their relationship is a lot less weird