 However, he had already begun to exhibit signs of literary talent, and his first novel "Kappan-ya no Hanashi" ("Tale of a Printer's Shop") was published when he was 16.This novel won a prize in a competition and was highly praised by the well-known author and editor, Kikuchi Kan.

Due to this encouragement, Nagai devoted his energies to writing, submitting a stage play to the Imperial Garden Theater in 1923, and publishing "Kuroi Gohan" ("Black Rice") in "Bungeishunjū," a monthly literary journal founded by Kikuchi Kan.In 1924, together with the famous literary critic Kobayashi Hideo and some others, he launched his own monthly literary magazine called "Yamamayu".