Sefure no Hinkaku

Sefure no Hinkaku summary:

Choko starts to have a friends with benefit relationship with her High School crush Kazuki. She is now 36 years old, twice divorced and has a teenager daughter who she raises on her own. Kazuki works as a doctor in a lady's clinic and also doesn't want to marry or have a deeper relationsip. They agree to just sleep with each other when one of them wants to do it. But of course, there are still feelings and other drama trying to break this promise. [MangaUpdates]