The approach is done with many calculations. Great.
I mean, like many mangas I've read - and with concepts that are not much different, about the age gap - this doesn't get a completely bad perspective. Even though it is understandable how people respond to illicit relationships between strangers. There is a feeling of anxiety, worry, fear - well, it increases.
But, the age gap is still not a big problem.
It is like I'm 21 years old and like men over 30 years old. There will be time for me to arrive at a certain age, as well as Satoko and Mashuu. That is not a crime. Don't compare it to hentai - which is clearly different, in a sense, in ethics.
There is no difference in terms, but there is a significant between the two. What is it? Whether or not there is commitment.
I will not openly say "there is no limit in love". Because, we humans still have to see, consider everything. And this has to do with how special this manga is because the main character is not a lonely woman who is thirsty for caresses of love - like a teenager blinded by love - and not too glorifying the beauty of love then filled with many aphorisms. They are met by the needs of each other. And that love comes slowly.
As of now, I think Satoko still doesn't feel 100% love. Not yet. She only recognized Mashuu as the opposite sex, as a friend.
It is clear the concept of love in this manga will be debated through social views. I expect the climax to fall in the right place.