As a result of Onmyoryo's policy to continue exclusive development of only 30 selected trainees to become hogi (gikan), the number of gikan in Onmyoryo and the number of posts in that office gradually decreased, while a power struggle among court nobles intensified during the early Heian Period of 9th century.
わずか30名の修習生にしぼって閉鎖的に方技（技官）の育成を続けた結果、9世紀の平安時代初期には、次第に陰陽寮の技官人材が乏しくなったと見られたことや、公家の勢力争いの激化にともなう役職不足も見られた。