Established Relationship

Rintarou (28) X Santa (32)
[Santa and Rintarou are what can easily be described as an old married couple. they have been together for a long time and the series explores what is their day to day life.]

This one is masterpiece, I've reread for bunch of times

Shima X Natsuo
[Ephemeral but beautiful days that are in danger of shattering... Shima and Natsuo lives in a normal countryside that you can find almost anywhere. They are normal high school boys that you can find almost anywhere. However, their blissful love is unique only to them and cannot be found anywhere else.]

Dating from the beginning
THEY'RE FLIRTING IN THEIR DAILY LIFE
THEY GAVE ME BUTTERFLIES HELP
My fav!

Been together for 15 years, and then had and arguments, Kusaka said "You broke our promise, so I'm breaking up with you" leaving Mikuriya flabbergated. But they overcome it clean and nicely.
I really love it!!! absolutely my favorite regret not reading this sooner
What the hell with the rating, it should be 9.7 dammit this is a freaking MASTERPIECE

Shiina (alpha) X Aoi (omega)
[Shiina and Aoi are a romantic Alpha and Omega couple who live happily together with their little son, Noel. Protected and sheltered by his parents, Noel is unaware that his family is different from any other until he one day accompanies Shiina to work and notices something strange. Why is it that he and Aoi are the only ones with cat ears?]

Omegaverse, married life

Wakabayashi Keigo X Onodera Yuu
[Yuu and Keigo are a happy couple of 10 years. They spend their days together like any other: wake up in the morning, eat breakfast, and go to work. Even in sickness and in health, you bet they’ll be smiling happily (and getting in their sexy time)!How do these two normal guys face the countless problems ahead and continue to spend their lives together? At the end awaits their future as a couple! A day in the life of a gay couple living together!]

Sei x Uito
[The ever cool and manly Uito has a sweet, cutesy side he shows only to Sei...! They don't miss an opportunity to smooch whenever their parents are out, and work hard on their finals and part-time jobs so they can live together one day. It's no surprise they go wild on their graduation trip...! Who fell in love first? This story follows two childhood friends who spend their school days totally besotted with each other! ]

Kaoru Niishibashi (23) X Seijiro Kishiwagi (25)
[Kaoru a professional baseball player and Seijiro a police officer are dating. One day Seijiro had a investigation and told Kaoru not to contact him, 2 months later, while Kaoru jogging to release some stress saw Seijiro in front of love hotel...
Seijiro appear as an ice-cold man but have a masochistic side.]

Short but i think this is good!

Tatebayashi Kazushige X Himemiya Shin
[Himemiya Shin has always wanted to become an actor ever since he was in high school. Now, he is an up and coming actor who only gets roles for the bad guys. Tatebayashi Kazushige has always wanted to go to college, but instead he became an actor. Now, he is an up and coming ikemen who only gets the likable roles. These two opposites may look like they have nothing in common on the outside, however, what secrets lay on the inside?]

Dating since high school

Kijoong X Bae Wooshin
[“I’m dreaming of a soap opera like love."
Wooshin Hyung replied with that line on the day Kijoong finally confessed to him. Kijoong initially thought that Hyung’s words had meant “be good to me”. But as time passed and he started to fully understand Hyung, he realized the true meaning that Hyung wanted their relationship to literally be like a soap opera.]

They're dating from the start. The uke's kinda weird but i still like it

Watanabe Ryusuke X Yoshikawa Haruki
[Yoshikawa Haruki has a crush on his Watanabe Ryusuke, his best friend since high school started.
Haruki is a bit relieved that Ryusuke is not good with girls, but suddenly a girl seems to have taken interest in him.]

They're dating at the end of the 1st chapter