This is mostly based on the summary quote by Samuel Johnson which I heard while watching Criminal Minds, causing me to become thusly inspired.
Recessional
In the early days, Yuzuki's memory bank tells her, there had been a time when she had tried so hard to be a sister to Minoru that, in all her effort to be, she had lost the effortless defining grace of her predecessor. Her boy's face back then had been a straining thing, endevouring to smile, pretending not to frown. While she would have done anything to cure it, in those days she was not a doll wired for free thought on anything but making him happy and, by doing so, inevitably making him cry.
(Yuzuki thinks one day, when there are cherry blossoms and sunshine and fragile spider threads, if she likes all these things because she was so fond of them. And if ever that thought made her sad, she brushes it off, because to be like Kaede is the highest honour her Minoru can give.)
(and all she is built to receive.)
Minoru keeps a steady distance from her after Yuzuki is made and keeps her name different in his mind so as not to get confused with this inhuman perfection that, for all the data in the world, is simply not the same. He tries not to get attached and in years this too will become a bitter dream.
(There are perhaps parts of Kaede that Minoru never knew, for everyone has hidden dreams. Yet it never crosses his mind for an instant that it is because Yuzuki has only such a surface personality that she feels so wrong.)
Their boat makes it's way down the cool, perpetual river and this is a pattern in which they continually indulge. Playing couples, pretending to be humans, acting as persocoms, being anything but themselves these days because it is all to commonly pathetic.
Yuzuki smiles from her place at the bow, pale polymer fingers trailing ripple waves in the water as Minoru rows along at a gentle pace. Perhaps they are close enough to touch each other if they wanted, perhaps they already are, but there is a comfortable peace between them in which she is no ones sister and he is the master of nothing at all.
(When they both stop trying is when they truly start to understand.)