How do you say yiff in Japanese?

Answer 1

If by "yiff" you mean a type of furry fetish, there are several ways to say it. "Kemune" are animal-people hybrids (so neko-kemune would be a fetish for cat-people, possibly furry ones.) There is also a slang for an otherwise regular girl who dresses up in cat ears and tail so she can be more wild in bed, she would be called a "neko-mimi" girl; I think this would also apply to other types of animals. Kemono-mimi is a compound word which is a more general term for these fetishes.

Common fetish anthropomorphs in Japan are cats, dogs, sheep, and bunnies. All of these are domestic animals, which appeals to the larger Japanese love of dominance/submission play. They also have cultural associations, for example bunnies are associated with the sexy women in "hostess clubs."