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 engrossed in home economics, he wears a serious but relaxed disposition.
- (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 appearances in the World Trigger calendar.
- According to volume extras he likes:
- Praising seniors
- Shōnen manga
- In His Character Profile, it was said he could have been the "honorary captain of Saeki Squad" but the quick raise for Kusakabe Squad made it complicated.
- In one of his birthday tweets however, it was said that he led his own squad.
- World Trigger Manga — Border Briefing File (p. 60)
- World Trigger Manga — Vol. 24 Chapter 206 (p. 20).
- World Trigger Manga — Vol. 24 Chapter 212 (p. 12-14).
- World Trigger Manga — Vol. 24 Chapter 212 (p. 12).
- World Trigger Manga — Vol. 24 Squad Profile
- World Trigger Manga — Vol. 24 Character Profile
- 2022 Birthday Tweet