Teacher-student love, happy ending:
Close Range Love (2014)
My Teacher (2017)
Another types of taboo love with happy ending:
King2Hearts (2012) [South Korea imagined Emperor & North Korean agent], there's also another one like that - something, something "... landing on you". Maybe "Crush landing on you"? A similar title, just don't remember it.
Come and Hug Me (2018) [psychopathic father of the ML killed parents of the FL many years ago when they were kids and in love, now a brother of the ML also wants to kill her, that psychopath escapes from prison targetting her as well so the kind-hearted ML who became a cop by overcoming his feeling of guilt and because he wants to be different than his father protects the FL, she has never stopped loving him, there's a happy ending and all, he doesn't kill his father nor brother even tempted to when they almost kill the FL, he's really a good, kind-hearted gguy totally opposite to his father]
The Liar and His Lover (2013) [please, watch the Japanese movie, not the Korean drama series. Drama sucks like hell compared to the original, sadly - because it could have been this one Korean drama about rock instead of shitty pop idols stuff - in the end, it wasn't, it was just about shitty pop idols :-P]