I was reading this manga when I stumbled upon an author's comment: http://mangafox.me/manga/dame_bl/v01/c010.5/7.html

Are there any mangas out their who has the plot like the one above?

I was quite blown away by the concept and was intrigued by the idea the author set up. I'm not real interested in reading straight girls falling for cross dressing boys (who still identify as male), straight males falling for crossing dressing guys, or straight males falling for tomboyish/butch females.

I guess I'm looking for mangas with the premise of transgender males attracted to females, transgender females attracted to males, or like the one above a gay man (or a lesbian) attracted to a transgender. I don't really want "light" or "comedic" storyline either. I'd prefer if the subject was treated with respect and more mature. A slice of life is fine.

The closest one I can come up is the manga above and Hourou Musuko [url]http://mangafox.me/manga/hourou_musuko/[/url]

Intersexuality - not transgender but close enough

Oh, when I read Dame BL I was also interested into reading a manga with this plot. Unfortunately, I was unable to find many manga like that, and none that actually addressed the subject, as you said, with respect and maturity.

Theones I can think of right now are those:
Ai no Shintairiku: Sara is the new girl at the school. Until recently, she used to live like a boy, but, much to her parents dismay, she identified herself as a girl and decided to live her life as one. In the school, she meets a boy who is interested in her, albeit confused by this attraction. This manga is very, very, very silly. It treats the gender issues in a fast and superficial way. It is still a nice try, I suppose. Not what you are looking for, since it's not mature, but it is kind of nice that this manga exists.
Kakumei no Hi: This one is VERY superficial and simple. The author did not aim into making a serious story. Basically, Kei is a very pretty boy who finds out that his genotype is female, even though his phenotype is male. He decides to be who he really is and undergoes surgery to become Megumi. Actually, this one does not address issues and is very light hearted. The motivation of Kei to undergo this transformation process is also very poorly developed. Don't get me wrong, I love this manga (I absolutely love the author), but it is, in a way, as silly as this first one.
Nobara (KUMOTA Haruko): (I assume you are ok with yaoi, since you were reading Dame BL). Mimi works in a crossdressing bar and identifies as a female. She is in love with Kaoru-chan, who is a gay male. Also, very light hearted, but it's a interesting story.

The only pearl I found that actually matches what you are looking for:
Mascara Blues's third story, "So I Can Be Myself - A Long Dream". Read the summary, it's the one which treats the subject in the most mature way. It is, unfortunately, a oneshot, so it lacks a better development.

I guess Bokura no Hentai?

Hourou Musuko is the closest I could think. Oops, sorry, I didn't see you already posted it.
I.S.
Houkago Hokenshitsu
F. Compo
Double House
Poor Poor Lips has a transgender character, but she isn't the main character (appears after chapter 50 or so)
maybe...
Also, Transgender/s category.

Thank you so much for the recommendations! I shall go check them out.

P.S. For anyone that is also interested in this type of manga, I was reminded of Divine Melody: http://www.mangaupdates.com/series.html?id=1285

Although technically not transgender either, it does deal with the protagonist changing into male to female and falling in love with at first a female character and then a male one. Still not what I'm looking for though 🤢

I second everything so far.
Um...I want to add Claudine...!
If I remember correctly, Shinshi Doumei † plays this for both comedy and drama. It's more of a subplot and doesn't really concern the main character....much.

I like my men androgynous.
I like my women androgynous.

In Mermaid Line there is a one shot called "Ayumi and Aika".

Ayumi wants to get married to her boyfriend but he tells her that he wants to become a woman.

(I referred to Aika in the masculine here because it got to confusing when referring to he in the feminine in this sentence structure...)

Try Shibutani-kun Tomo no Kai, a little spoiler about it to see if you want to read it:

There is a transgender (mtf) character that gets involved with another boy, but not in a serious relationship.

Half & Half may fit, since it's about a straight girl who discovers her first love is now a transgender woman but still falls for her nonetheless. I think is a great shoujo, but didn't like the ending much.

Quote from CynicallyOp

I second everything so far.
Um...I want to add Claudine...!
If I remember correctly, Shinshi Doumei † plays this for both comedy and drama. It's more of a subplot and doesn't really concern the main character....much.

i also recomend Claudine...! however this one is Shounen ai.

Besides the ones that were already recomended the only transgender I remember is Click, and on a more comedic tone Kakumei no Hi

Try Genkaku Picasso, vol. 2, chapter 4, I guess! In the spoiler below I give small details about the story (they are not big, but it would be considered a spoiler anyway, since reveals details about the story... also, I'm posting this on this thread, so I'm already revealing there is a transgender character in this manga... anyway):

There is a story in ONE of the chapters of this manga, with a transgender (mtf) character. It is lovely, you should give it a try. It's in the second volume, the chapter is called "Hishida's Holy War".