Our deity created this world in a single day. Although we use the word "tree" in our "Tree of Life", nothing is beyond its powers. And, of course, he created the female of the Kappa species. Finding existence tedious, the female Kappa began a search for the male Kappa. And our deity, taking pity on her lamentations, took her brain and made of it the male Kappa. Then, giving this Kappa-couple his blessing, he said to them, "Eat. Have union. Live life vigorously".'— From Kappa by Ryunosuke Akutagawa
Kappa by Ryunosuke Akutagawa (author of Rashomon) is a sort of a Japanese version of Jonathan Swift's Gulliver's Travels. The narrator in Kappa loses his way in a fog while trekking through the Azusa valley towards Mount Hodaka. On the banks of the river Azusa, he sights a "Kappa" and in his attempt to capture this strange nimble creature (face like a tiger, beak, webbed hands and feet, oval-shaped saucer on the head, skin that changes color according to the surroundings), falls down a hole and ends up in Kappaland. Kappa is a narration of his experiences and adventures in this land which serve Ryunosuke Akutagawa to hold a mirror to Japanese society and culture.
In the extract quoted in this post, a Kappa elder tells the narrator the story of genesis according to Viverism, the Kappa religion — how their deity, the "Tree of Life" created the Kappas.