I'm looking for romance manga with a significant age gap between the couple?
Not a simple gap like 9 years (or such), but something well above 10. Like, 20, for example. Also, this "older" man should please look his age, with wrinkles or something like that. I don't want the manga to say he's 40 years old, but then he looks 20 and no older than his romantic partner. This is literally the biggest point: HE HAS TO LOOK HIS AGE!
And, please, dear lord, no loli or shota partners. I don't mind if his romantic partner is a little young (plus-minus 18), but not if they look like they hadn't even reached puberty.

No Tragedy either.
Also, no hentai, please. (However, I don't mind smut.)
I don't mind yaoi either, but no Naono Bohra works (I already read all her works).

Examples:
Jinbe
&
Miman Renai
Kore wa Koi no Hanashi
Nocturne (PARK Eun-Ah)

(My favorites: )
Ojikoi
Otoko no Isshou
Ristorante Paradiso
Mitsu-Koi
Tomodachi no Papa - Hakui no Oji-sama
Shuuden na Kankei
Harem Days
Hada no Ue no Renai Jijou
Renai Nenrei
Pillow Talk + Holiday
Zurui Otoko (NAONO Bohra)

Also, seeing as I know I'm not the only one who struggles to find things that fit my taste, I advice those who like these manga, you should take a look at FR: Pub Encounter on your play store. 😉 😉

Usagi Drop

Does she get older as the manga continues, so she doesn't look that young? 🙁 🙁 🙁

Quote from BlackLip

Does she get older as the manga continues, so she doesn't look that young? 🙁 🙁 🙁

Yeah.

At some point it does a time skip. (don't remember the exact volume) You find out Rin who was being taken care of by Daisuke has fallen in love with him.

Awesome, thank you!
I'll check it out!

Pretty sure there is at least one other thread about this (even down to the fact that the age gap should be significant), you should look it up :3

Indeed, I have been looking at those forums everywhere, but unfortunately, I've already read all the suggestions given.

I'm not sure there is more to read unfortunately (in the translated shoujo/josei area, at least). BL is another thing, but I can't really help you there, I don't know another mangaka that draws older men aside from Naono Bohra. I casually looked through my completed list and came up with this:
The Day and Night of a Competent Chairman
Otona no Mondai - this is not BL per se, the relationship is between MC's father and a younger man and the plot is about main character kind of coming to terms with his father's homosexuality, but I like it so... here you go
Your Honest Deceit kind of?
Honto no Uso
Bamford Koushakuke no Shitsuji
If you can read japanese there are a lot more titles to chose from. For example Love, Hate, Love. There is even a web magazine Oyajism specializing in the "young female older male" trope.

I hope my answer was at least a little helpful :3

Aw... damn... I figured that was the case, but I thought I might as well give it a try, you know?

Oh, awesome! I'll give those a try! Thanks for the help!
Haha... I completely forgot about Bamford Koushakuke no Shitsuji. I love it, though, so thanks for bringing it back to my attention.

Unfortunately, no, I can't read Japanese. I've begun to study it, but haven't gotten anywhere close to that good. 😔

Hana wa Saku ka is a yaoi manga with a relationship between a 19 year-old and a 38 year-old and it's a really very lovely (slow burn) romance. Also, I'm bookmarking all of your favorites because I love age gaps too!

Otokogokoro fits. Yaoi.

Businessman seme and young college uke. I believe the seme is in his late 30s and has a few eye wrinkles to show it.

Damn cute story