As the Spirit-sama Says

Episode 40: Elf Racing

Here is a certain stadium.
It is a place where one captures wild elves, trains them, and have them contend against each other in a contest of speed.

It was a popular event amongst the populace where it was fine to simply watch the naked elves running with all their might, as well as to place bets on which elf would win.

Lately, in order to produce even faster elves, there have been experiment with breeding speedy elves with each other in the aims of creating a child. Because of such, it would appear that owning an excellent elf has become a sign of status among the wealthy.