Onmyōdō and Abe no Seimei

Abe no Seimei never headed the Onmyōryō: performing the henbai for the emperor in 1000 he held no bureau post, and he reached high rank only after sixty.

Shigeta Shin'ichi, 'A Portrait of Abe no Seimei', Japanese Journal of Religious Studies 40/1 (2013) pp. 77-97: abstract, p. 78 (Gonki, Chōhō 2.10.11) and his table of Seimei's offices

Japanese court divination, calendar and directional taboo, held for centuries by the Abe and Kamo lines.

Sources2 sources

Scholarship

Shigeta Shin'ichi, A Portrait of Abe no Seimei, Japanese Journal of Religious Studies 40/1, 2013, pp. 77-97; p. 78 on the Gonki entry for Chōhō 2 (1000).10.11Seimei (921-1005) performed the henbai for Emperor Ichijō in 1000 without holding a post in the Onmyōryō; Yukinari called him the preeminent practitioner of Onmyōdō; he reached prominence and high rank only after sixty.
who was not an officer of the Onmyōryō
Hayashi Makoto and Matthias Hayek, Editors' Introduction: Onmyōdō in Japanese History, Japanese Journal of Religious Studies 40/1, 2013, pp. 1-18; pp. 7-9The Onmyōryō as a state organ, its passage into a hereditary Way held by the Abe and Kamo, and Seimei's place in setsuwa tales and the modern Seimei boom.
the hereditary appropriation of the “Way” by the Abe and Kamo families