Majo no Jouken

Michi, a 26-year-old high school math teacher, tentatively accepts her boyfriend's proposal of marriage, uncertain of her love for him, but feeling pressure from her father and society to do what is expected of her.
Hikaru is a 17-year-old boy frustrated by his home life with his single mother. After being expelled from many high schools for bad behaviour, he enters Michi's class as a new transfer student.
As their relationship grows, they realize they both feel they've lost themselves to the pressures of those around them, and it is this common bond that draws them dangerously close. What follows is a heart-wrenching story of forbidden love where Michi must face society's judgement for corrupting a minor, abandoning her fiance, and disappointing her parents and co-workers.
(Source: DramaWiki)