The plot and the art are absolutely fantastic.
I'm sure the mangaka didn't actually want to us think this, and probably because they couldn't make the manga longer. But I feel like at the end, the humans are just like a replacement. When they call Mashiro endlessly times Kuro, or when they talk about each other as they were Kuro and Rui!android.
So I think the part that is missing is both of the falling in love with they real personalities, attitudes and every little detail of each other.
Monokuro Limit