Bakuon!!

Why is a 40+ year old woman allowed to still attend high school?

Because

Okay, then why wear the helmet?

If her skin is so smooth and youthful that her arms and thighs give away her age, I doubt her face would.

She's undead.

I see

She's an insurance policy

Letting high school girls drive around on motorcycles without adult supervision is a horrible idea. So the school allows her to stay to serve as a protector of sorts for the girls, to be the experienced member they need to avoid fatal accidents.

How else would she be able to fuck younger girls?

It's their teacher that wants to fuck students, not Raimu-senpai

Raimu only fucks bikes.

Raimu doesn't fuck, she dominates