Manyoshu is the first major Japanese poetry collection and the subject of investigation by Tomitsu Okasaki. He does not explore the poetic value of the work but aims to highlight the philosophical, religious, and cultural-historical studies during the Manyoshu period through the selection of quoted poems, providing a reflection of that time. Okasaki also examines the compilers and the textual history of this collection, investigating the philological and historical phenomena, the geographical aspects in Manyoshu, and references to fashion and customs. In the end, he provides an overview of the poems and analyzes the currents of the time in comparison to the modern era.