Saeki has black hair parted in the middle (with the rest swept briskly over to the left), standing at a height just under Satomi. His high-collared uniform is black except for an olivedrab color on the biceps and chest pockets; it has white stripes running down the sides, as well as a white stripe lining the zipper. The Kusakabe squad logo is located above his left chest pocket.
He is not hesitant to speak his mind, or even question his captain — the former of which rings especially true when it comes to the cooking ability of other agents, much to his enthusiasm. When not obsessing over home economics, he wears a serious but relaxed disposition.
For much of the most recent season, his squad (along with Katagiri Squad) went scouting for potential recruits outside of the prefecture.
- (Reacting to Squad 2's supper during Phase 1)"Dang! Ikoma's a secret chef? Style points for him!" 
- Saeki and Uno first appeared in Chapter 180, without it being revealed who was whom; their names were matched to their appearance in the World Trigger calendar.