You know this one. In the current timeline, Usagi, Miyagi, Isaka, and Asahina are all 30+. Hiro is pushing 30. While he's only briefly in JJR, Kirishima (Japun's editor whose relationship is shown in Sekaiichi Hatsukoi's manga + light novels/movie) is in his 30s.
A thirty-year-old man falls for the young, sweet bartender at the bar he frequents.
A man awaiting cancer results sees an omen in a black cat and a young man who looks exactly like a friend he lost several years before.
Might be slightly confusing if you read too quickly, but this is really cute. Probably both in their 40s.
This one hurts. An on-again/off-again relationship between two people who don't seem to be able to forget one another. Spans two titles. It does end well but oof.
Going by memory, the characters are in their 30s
A man returns home to help with his ailing father's welding business and falls for Maki, his dad's right-hand man. Maki is 35.
Friends of 15 years get together when one is threatened with an arranged marriage, leading the other to confess. They're both 31.
The love story of childhood friends turned yakuza and lawyer, both 37.
Twenty-two years after they fell in love in college, two 40-year-olds are divorced by their wives and get a second chance.
At 39, Ei is a successful researcher and still being pursued by 32yo Gin, a boy he met when they were 15 and 8. They are occasional sex partners, but Ei, who is terrified that his reputation of being openly gay could harm Gin in any way, refuses to acknowledge Gin as his lover and repeatedly tries to push him out of his life.
Ei will frustrate some readers, but I find him relatable. Head's up for dubcon. And if switching is your thing, check out the doujinshi.
Multi-generational story of a family cursed with the supernatural power of kotodama and the paper dolls - kami - who accept their wounds. Genma is middle-aged in the present timeline. Asari, while he doesn't physically age, is the oldest kami and must be 30+. Waki is the oldest living character; we don't know his age.
Head's up for dubcon early in Genma's story. The twins & sister skeeve me out; I skip their scenes. Asari's love story is the best.
Junjou Romantica