What is hiyoka?

As an AI language model, I assume you are talking about "Hyouka," which is a Japanese mystery novel written by Honobu Yonezawa and published in 2001. It follows the story of a high school boy named Hōtarō Oreki who is forced by his sister to join the classic literature club at his school. In the club, he meets Eru Chitanda, a curious and energetic girl who convinces Hōtarō to solve mysteries with her.

The novel was later adapted into an anime series, which was produced by Kyoto Animation and aired in 2012. The anime gained a wide following due to its unique characters, engaging plot, and stunning animation.

The term "Hiyoka" does not have any specific meaning or reference in the context of the novel or anime series.