As iterated many times in the comments, the manga is pretty unrealistic. the plot, characters and development is really flat. Right from the beginning, Fukami falls head over heels for Risa and he remains this way for the rest of the manga. to fully enjoy this manga, you need to temporarily suspend belief and remember that these characters live in a perfect utopian society and literally have not a single ill-intention bone in them.
in a nutshell, this is the perfect fluffy sugar daddy fantasy. Fukami literally lives and breathes for Risa. He spoils and pampers her like crazy and would 100% kiss the ground she walks on if she asks. the drama is also super tame and usually solves itself in the end because Fukami is two steps ahead of the plot and everyone in it. in fact, the drama somehow always ends being sugary and diabetic. the smut is also very tame (they have a lot of sex) but somehow it's executed in a way that it's not distasteful? it can get shamelessly sweet and a little cheesy.
that being said, I give it an 8/10 because the art is beautiful and it's a light and enjoyable read. the series isn't plagued by drama that drags on for ages and sometimes, I wish I could be Risa and have myself a Fukami. I think Coffee & Vanilla does exactly what it intended to do from the beginning: create a fantasy of a younger woman being taken care of, spoiled, loved and pampered by a rich, and powerful older man. it's not meant to be a serious/realistic portrayal of relationships and society. it's almost like a 50 shades of grey but without all the social/physical manipulation, baggage and psychological torture. instead, you have a cup of straightforward, wholesome sweetness. i would recommend this manga for shoujo/josei lovers looking for an easy and stress-free read. like someone else said, you can easily substitute yourself as Risa since she lacks any notable characteristics other than being demure, innocent and girly.