And I'll state this now, but no hentai, yuri, or ecchi. I'm fine with smut though if that makes sense.

So basically, a forbidden type of love I suppose? Forbidden is a bit strong, but I'm not sure how to word it.

Yaoi/Shoujo-ai is fine, but I'm not looking for characters who are in love with someone of the same sex and angsting over it.

Nor am I asking for incest or an age gap between the couple either.

To be specific, the main character has to be in love with someone they're not suppossed to be in love with. For example:

-in love with their mom/dad's lover.

-in love with someone who is already married.

-someone who already has a boyfriend/girlfriend Strobe Edge is a good example and also one of my favorites. ^^

-a boy/girl who falls in love with their girlfriend/boyfriend's best friend.

-a girl in love with her sister's boyfriend/fiance

-a boy in love with his brother's boyfriend. Punch Up! is another good example since he used to love him.

-a servant in love with their master/mistress, but their social standings are too far apart.

I guess another way to best specify this request is basically "someone they can't have." Not due to gender, incest, or age gaps, but because the person they want is someone who is already taken, not within their reach, or simply because it would be socially-wrong to pursue their love interest.

It can be yaoi, shoujo-ai, shounen, seinen, josei, or shoujo.

[img]http://i32.photobucket.com/albums/d25/khmershinobi/b750d351697e8dd4b2600bce2a15e1e9-2-2.jpg[/img]

__ I'll have what she's having... please~♥

Quote from khmershinobi

Not due to gender, incest, or age gaps, but... because it would be socially-wrong to pursue their love interest.

A bit contradictory here, lol...

Your criteria for what's an acceptable brand of forbidden seems pretty arbitrary...

Basara - http://www.mangaupdates.com/series.html?id=264
MC is in love with her enemy

Mukizu ja Irarenee - http://www.mangaupdates.com/series.html?id=4754
They kind of just make each other feel like it's impossible to be in the relationship because they don't want to hurt someone else. It's a yaoi.

Sarashi Asobi - http://www.mangaupdates.com/series.html?id=25344
Shinigami in love with human

Kanata Kara - http://www.mangaupdates.com/series.html?id=4875
The male MC is said to become the sky demon when the awakening comes into his world and he falls in love with the awakening.

Edo Karuta - http://www.mangaupdates.com/series.html?id=46061
Story 4

Shadow of Visions - http://www.mangaupdates.com/series.html?id=2791
Ibara no Okite - http://www.mangaupdates.com/series.html?id=41967
Evyione - http://www.mangaupdates.com/series.html?id=21445
The Great Merchant Kim Manduk - http://www.mangaupdates.com/series.html?id=54645
Oiran Girl - http://www.mangaupdates.com/series.html?id=58619
Maiden Rose - http://www.mangaupdates.com/series.html?id=1817
Roman Gousha - http://www.mangaupdates.com/series.html?id=6831
Kagerou Inazuma Mizu no Tsuki - http://www.mangaupdates.com/series.html?id=6321
Snow Drop - http://www.mangaupdates.com/series.html?id=1485
Sekai no Hate - http://www.mangaupdates.com/series.html?id=67069
Akatsuki no Miko - http://www.mangaupdates.com/series.html?id=80551
First Love - http://www.mangaupdates.com/series.html?id=22382
Bónd(z) - http://www.mangaupdates.com/series.html?id=3810

Remembrance, a forsaken thing that revokes ignorance and leaves people in doubt, is my only redemption and solace deep within the cascade of white.

The evergreen trees speak of days long past when music mingled with the wind and sweet murmurs brushed our cheeks.

Do you care if it's fulfilled in the end or not?

Quote from jedinat

A bit contradictory here, lol...

Your criteria for what's an acceptable brand of forbidden seems pretty arbitrary...

Lol sorry about that. I'm aware of the contradiction, which is why I tried to be specific by using a few examples.

Quote from OrchardPetalLullaby

Basara - http://www.mangaupdates.com/series.html?id=264
MC is in love with her enemy

Mukizu ja Irarenee - http://www.mangaupdates.com/series.html?id=4754
They kind of just make each other feel like it's impossible to be in the relationship because they don't want to hurt someone else. It's a yaoi.
...

Oh, wow! So many titles. Thank you so much. I'll definitely look into these. 😀 And thanks for reminding me about the MC being in love with their enemy. I love stuff like that.

Quote from ImaginaryWishes

Do you care if it's fulfilled in the end or not?

Nope. Doesn't matter whether it's fulfilled or not. Unrequited is a plus too actually, and I didnt' think about that so thanks! XD

[img]http://i32.photobucket.com/albums/d25/khmershinobi/b750d351697e8dd4b2600bce2a15e1e9-2-2.jpg[/img]

__ I'll have what she's having... please~♥

Tsuki no Waltz 2nd story
Half and Half is pretty weird, but I suppose it fits.

Blanc Marie contains smut and...well, not sure if you'll like it.

Reimei no Arcana
The marriage & master/servant & social standings ("races")

Watashitachi no shiawase-na jikan
Not any of the suggestions you listed, but the love is something that can't be fulfilled