Im looking for a manga, I believe it was partly NTR. Story went where a boy found out the woman he loved, teacher/nurse, was being blackmailed by a coworker and so he beat the crap out of the guy and told the woman she wouldn't be bothered by him anymore. Sorry its vague but it was one of the many NTR manga that I sorta enjoyed due to the fact the main character actually did something about it.

The only that i saw and ended with a picture that the boy bashed the blackmailer is in this tank
Ana no Oku no Ii Hibu chapter 2-4 Gibo.