While talking through PM with someone, a story came up that interested me, though they did not tell me the name. It's NTR in which a boy's girlfriend is blackmailed into doing it with her teachers. She breaks up with him because it feels even worse to be doing it behind his back, so she prefers to "free" him. At the same time, she secretly builds up evidence the whole time and exposes everything during graduation. This sounds interesting, like one of the very few NTR that end well (she apparently gets back together with the boy at the end), so if anyone knows the title or the author that'd be great.