During his days at Teikyo University, Saeki rented a room in the art club where he learned the basics of drawing on his own with the desire of making anime.
[1] He started as an in-between animator at the studio in 1996, and in 1998, the 25th episode of Cyber Team in Akihabara marked his first storyboard credit,[2] and the following year marked his episode director debut and scriptwriting debut with Kare Kano,[3][4] where at-the-time fellow Gainax director Hiroyuki Imaishi described that the both of them had "learned our chops.
[11] The following years saw Saeki working mainly as a storyboard artist, scriptwriter, and episode director for Shaft and Gainax series, and notably became an essential member of Hiroyuki Imaishi's team on Gurren Lagann.
Beginning in 2017, due to Gainax's minimal production output, Saeki began providing storyboards as a freelance artist.
[17] According to animator Kazuya Shiotsuki, Saeki's prominence at Shaft has influenced the younger staff at the studio alongside Yasuomi Umetsu.