Sayoko Shiki/Plot

Background
Shiki joined Border roughly two years before Yūma Kuga and Chika Amatori. She has been a Hikikomori for an unknown amount of time, and she lived on pickled kelp and water sent to her by her family when Kumagai scouted her. Since joining Nasu Squad she has her financial situation in check and has taken to shopping online. Shiki is the one who designed the uniform of Nasu Squad, which earned her the praise and respect of some male agents.

Introduction Arc
Nasu Squad presumably takes part in the extermination of all Rads in Mikado City.

B-Rank Wars Arc
On February 1 Nasu Squad is assigned to defense duty.

Round Two
On February 5, Nasu Squad fights a rank war against Suzunari First, Urushima Squad and Kakizaki Squad. They force their opponents into a melee and manage to score two points, but are unable to defeat Kō Murakami, marking their sixth consecutive loss against Suzunari First.

Round Three
Two days before her squad's match against Tamakoma Second and Suzunari First, Kumagai and Nasu meet at the latter's house to prepare a strategy while Shiki corresponds through her computer. They discuss the footage of Yūma's solo matches against Murakami and his abilities compared to his teammates'. Kumagai is more concerned about Suzunari First, against which they have lost six times in a row. Shiki remembers that Suwa Squad defeated the team by remaining in Gunner range, so they decide to base their strategy on Nasu and pick a stage that facilitates it. The following day, Hiura tells them that she was unable to dissuade her parents from moving after she graduates middle school, prompting Nasu to swear they will climb up the ranks before she has to leave.

One day later, on Saturday, February 8, the four members of Nasu Squad recap their strategy minutes before the match. Once again they resolve to advance in the ranking. After the match starts and the bridge is destroyed by Chika, Shiki relays the information to her captain and tells Hiura to hide. When Taichi Betsuyaku snipes at Nasu, Shiki sends her a 3-D image map to help her shoot back. She observes anxiously when Hiura decides not to bail out but to face Yūma head-on. When Nasu switches to cornering Tatsuya Kuruma with her mobility, she instructs Shiki to keep an eye on the members of Tamakoma Second. Shiki congratulates her when the match is over. The four members of the Squad resolve to keep trying to reach the upper tier of B-rank.

Galopoula's Invasion
On February 19 Shiki supports Kumagai and Nasu as they engage Wen Sō. When the latter activates Servitora, however, Shiki notes with panic that Radar detects multiple trion signatures.