Looking for specifically manga that takes its yuri slowly as opposed to being too fluffy or having too much of playing misunderstandings as comedy; something like Sasameki Koto, Octave, Aoi Hana, or Kashimashi, perhaps?
It sounds like you’re interested in yuri with a lot of chapters, but I think Sasameki Koto, Aoi Hana and Kashimashi are the longest yuri I can think of, haha. Other not-too-fluffy, not-too-jokey manga, hmm…
Here are some other nice long yuri manga that are completed:
- Hanjuku Joshi (NSFW) by Morishima Akiko
- Girl Friends by Morinaga Milk - Licensed and printed in English! I’d recommend buying it.
- The Secret Recipe by Morinaga Milk
The thing about long manga is that a lot of them are still in progress! Here are a few that are ongoing:
- Kase-san by Takashima Hiromi
- Citrus by Saburouta - It’s been licensed and will be printed in English soon! Support your local yuris!
- The Feelings We All Must Endure (NSFW) by Amano Shuninta
And some shorter series that I think still capture the feeling you’re looking for:
- Lonely Wolf, Lonely Sheep by Mizutani Fuuka
- Cirque Arachne by Saida Nika
- Green by Ootomo Megane
- Ebisu-san and Hotei-san by Kizuki Akira and Satou Nanki
- The Flower and the Star by Suzukin Kario
I hope that’s enough for ya!