I'm looking for drama/movies that tells how two people fall in love and be together in a pure way despite the condition they're in. What I mean by not-so-ideal setting is something like a taboo relationship (infidelity, teacher-student, incest etc) that seems pure despite the stigma, or simply two very damaged people who find their salvation through each other. The taboo (or whatever issue they're dealing with) has to be dealt seriously and not sugar-coated, yet the 'love' itself is pure. I'll leave the 'pure' interpretation to you guys, because what I'm looking for is not a love story devoid of sex, but it's more about the vibe and impression. For example, something like k-movie Our Happy Time. I'm fine with dramas from any country. 

Thank you for your recommendation ~

Transit Girls is just what you're looking for in my opinion.

Na Ra's Rain
Ordinary Love
Taste of Curry
Somewhere I Have Never Travelled

I would explain what the issue is with each but it's a huge spoiler for some of them. Also do they need to end up together? Because in some of these they don't. Let me know if you want me to tell you either way!
Heart to Heart
Mars
Romance
Seven Days: Monday - Thursday (and then its sequel)
Pained
@versaillesyoo: thank you~ nope they don't need to end up together, and no spoilers! I like to experience the twist and turn myself :3

@pigtails4ever: thank you, I've put Mars aside for so long despite recs and reviews, probably should try it now
Boku no Ita Jikan
Ho Goo's Love
Hello, God
Good Doctor
Pride
My Love Eun Dong
Kurosagi
Mitsu no aji - I always saw it as pure (real, true) love even though the man she loves is her father's younger half-brother.

Koukou kyoushi 2003 - teacher/student with a strange twist I've never seen anywhere else; it was so very wrong and yet so, so right in a way I can't explain but felt with all my heart.

Kimi wa petto - I wouldn't have thought about it if I hadn't seen it suggested above but I actually agree. The setting is not so ideal, and it's about damaged people. This one is the lightest of the three.

(I think Boku no ita jikan is also very good, but somehow I wouldn't think it belongs in this group of stories. It's true that the setting is not at all ideal, and there is romance but I wouldn't call it taboo or finding salvation through each other. I could be wrong. I loved it though!)
Kono yo no hate
MARS
Lipstick
Kamisama Mou Sukoshi Dake
One Million Stars Falling from the Sky
Ooku: Arikoto Iemitsu Hen
Aoi Tori
Majo no Jouken

All these are perfect example of what you're looking for. ;)
Pick one and enjoy. I love them all with Kono yo no Hate and MARS being my favourites. And it's totally logical all of them come from Japan except MARS. Japanese are the masters of those kind of dramas. ♥
If you haven't watched In the Mood for Love, you should definitely give it a try :-) It is a classic.
And in my opinion a beautiful example of pure but tragic love.
Mars
Byakuyako
Heart to heart
Also the princess' man
Add: Sore demo ikitte yuku



Sorry but this will be easier if we could edit the posts :(