Here are a few that vaguely work with your realistic romance requirement... because almost all the stories that I've read, with contain any romance, are far from realistic.
Always Together--This is a must read for a realistic love story.
18-sai no Kodou--Sometimes a relationship doesn't work as well as you hoped, and sometimes there's one that just might.
3 Years--It's sometimes a bit much... but with this one it has such a grain of truth in it. If you don't chose, you lose, and you have to deal with that.
Ii Hito--This one is vaguely realistic in the romance part, but it tries to show how the female characters that are slightly attracted to the main character deal with their rejection. Also, when it has a flash back to the main character's relationship with his girlfriend it seems fairly plausible. However, it is rather long and the distance between the romance parts are few and far between.
Cousin might work, but there aren't that many releases yet so it's hard to say.
So, out of 197 romance series... I have about 4, maybe 5, that are sorta realistic.
Check that... I only have 152 that I have read or am reading, and the rest are on my wish lists.
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"Officially, this machine doesn't exist, you didn't get it from me,
and I don't know you. Make sure it doesn't leave the building."
So I'm going to suggest a few that have given me the same sort of feeling - not sure if they're what your looking for but in looking at your lists we seem to like a lot of the same mangas:
