Laws in these regards are mostly "grey area". Drawn teen guy porn is still drawn and fictional art. There might be other laws that can be interpreted to ban things like this, but really nobody cares. I don't think a single person was ever prosecuted (outside of countries like saudi arabia ofc) because of having drawn teen porn on their computer.
And thus I personally don't care about laws but about my own moral. I don't mind fapping to images/drawn art of teen guys just a few years younger than me, but I DO mind, if the depicted person is obviously a child. And as this is all fictional stuff anyway, I don't care about the age of him in the series, but about how old he looks in the respective images.