Seito taishogun (literally, great general who subdues the eastern barbarians) (征討大将軍)
The term "Seito taishogun" is the title for general which was used in China and Japan in the past. It was one of the many titles of taishogun (great general) and was used on an ad-hoc basis.
The first Seito taishogun in Japan was Waobu, one of the five kings of Wa (Japan). In April 502 when Lian dynasty (Nanchao) was established, king of Baekje Yodai, who had been appointed to Chinto taishogun by the former dynasty (Qiguo (Nanchao)), and Waobu were appointed to Seito taishogun. However, the above appointment was made based on the Chinese system and in Japan, it was nothing more than the title and ranking given by China.
Taishogun in the Nara and Heian period
The Japanese Ritsuryo code had stipulations for taishogun in Gunboryo (the Statue on Military Defense)
During the Nara period and the early Heian period, taishogun with various titles were nominated on an ad hoc basis as a commander-in-chief in the war occurred in remote regions. Seito taishogun was one of them and KI no Kosami was appointed to Seito taishi in 788. Taishi is a synonym to taishogun.
Later, FUJIWARA no Tadafumi was nominated in 940 in order to search and kill TAIRA no Masakado, who rebelled in Kanto region.
In the end of Heian period, MINAMOTO no Yoshinaka (Yoshinaka KISO) was appointed to Seito taishogun (some studies say he was Seii taishogun (literally, great general who subdues the barbarians)).