u/Dampston

It's about a magical girl and her manager.

In the story, the older a magical girl gets and the longer she uses her powers the stronger the (I guess you could call it recoil) from using their powers.

For this magical girl, it's being horny. Her manager is there to manage her horniness by having sex with her.

I remember the magical girl wearing a school outfit (I think) when in magical girl form, and using a Katana.

I think there were 1-2 chapters.