Ehhh, that's kinda iffy on the statutory rape thing. For one thing, he's at least 16 based on his grade. That's around when guys reach sexual maturity. This isn't some 12 year old kid who maybe hasn't even learned what sex is yet. If you age both characters up by even 2 years, it would be eyebrow raising, but not actually illegal by American standards.
By Japanese standards it's already legal with no age adjustment. On a less serious of an answer note, the adult woman screwing the highschool boy is basically never caught because the guy felt traumatized by the experience and came forward. They get caught because he's a stupid fucking teenager who couldn't keep his mouth shut to his friends and just had to brag.
That being said, I only got so far as to confirm his age before backing out, the premise doesn't really interest me.