Like the title :) I've seen one or two similar dramas but then the ML wasn't the "teacher" and her true new love interest was someone else. 

Are you asking for titles where a teacher and student get involved without realizing that they are student and teacher?

 Baqa:

Like the title :) I've seen one or two similar dramas but then the ML wasn't the "teacher" and her true new love interest was someone else. 

Daytime Shooting star ;Hirunaka no Ryuusei 

drama : https://mydramalist.com/20736-daytime-shooting-star

manga : https://myanimelist.net/manga/27231/Hirunaka_no_Ryuusei

 Ichika Kaneki:

Daytime Shooting star ;Hirunaka no Ryuusei 

drama : https://mydramalist.com/20736-daytime-shooting-star

manga : https://myanimelist.net/manga/27231/Hirunaka_no_Ryuusei

here the ml was the teacher. got more screen time ( in movie) and lot more panels in manga than the guy she ends up with. but she just doesn't end up with the ml.

 Baqa:
Like the title :) I've seen one or two similar dramas but then the ML wasn't the "teacher" and her true new love interest was someone else. 

Since you put "teacher" in quotes, I'm assuming you don't mean that the ML love interest has to literally be a teacher.

In these dramas, the FL was hurt by a love interest in the past or was naive / uncertain / confused by love until the ML (who is confident in romantic situations and / or sure of his own feelings for the FL from early on in the drama) comes along and "teaches" the FL to let down her walls / open up / enjoy being loved and being in love:

It's not that I can't marry but I don't want to

Sry if I was ambiguous, but I ment teacher as in the sense of a teacher of love :)