Wikipedia
The is the oldest collection of Chinese poetry ( kanshi) written by Japanese poets.
It was created by an unknown compiler in 751. In the brief introductions of the poets, the unknown writer seems sympathic to Emperor Kōbun and his regents who were overthrown in 672 by Emperor Temmu after only eight months of the rule. Thus, it has been traditionally credited to Awami Mifune, a great grandson of Emperor Kōbun.
It is a collection of 120 works by 64 poets written in the elegant style of poetry popular in China in the eighth century. Most of the poets are princes and high-ranking regents, such as Prince Ōtsu. Eighteen of the Kaifūsō poets, including Prince Ōtsu, also have poems in the later anthology of Japanese poetry, the Man'yōshū.
At the time Kaifūsō was written, Chinese poetry had a higher place in the Japanese literary world than waka, and Chinese characters were used for official documents. Most of the works collected were read on a public occasion.