Distant water is bitter
There once was a boy born from a peach that had floated down the river; his foster mother charmed it to her hands with a nursery rhyme. Koumyu sang the rhyme over the baby's cradle and told the story to the toddler too fretful to sleep. Baby, toddler, and boy had the same cranky, combative look, as if hunger, sleep, and adults were expected and unworthy enemies. He never asked the obvious question, so Koumyu found other ways to tease. Bitter as a peach-pit, that boy; but pits are seeds. One day he'd find a sun to grow him sweet.
The near water is sweet
There once was a boy born not from a peach but from the earth itself. You could say he had a mother, but not one whose gifts included fairy tales or nursery rhymes. Sanzo's inclinations didn't run that way, either; the only person who ever explained things was Hakkai.
Goku turned the peach over in his hands, puzzled. "So it grows from the earth. Like I did."
Gojyo stole it and tossed it up in the air. "Gimme another, I'll juggle -- hey, does that mean when Goku eats fruit, it's cannibalism?"
"It is not!"
Sanzo's first bullet hit the peach.
Notes
I'm hoping "myth" is loose enough to encompass fairy tales; if it's not, let me know. You can find
"Momotaro, or The Peach Boy" at Project Gutenberg.
The nursery rhyme is:
Distant water is bitter,
The near water is sweet;
Pass by the distant water
And come into the sweet.