Four poets of the period of the Northern and Southern Courts were described in "Ryoshun IMAGAWA's Kagakusho (a book on the study of waka poems)" and "Shotetsu monogatari (Tale of Shotetsu)," and were called "The Four Heavenly Kings of Waka among followers of Tameyo" of the poet-monk Nijo school.
南北朝時代の4人は『今川了俊歌学書』『正徹物語』などに記されており、歌僧二条派「為世門の四天王」と呼ばれた。