Shiori Usami/Plot

Background
Before joining Tamakoma Branch, she was part of Headquarters. Two years before the start of the series, she was the operator of Kazama Unit during its early years.

Black Trigger Retrieval Arc
Usami introduces Osamu, Yūma, Chika to Tamakoma Branch. There, she mentors them about Rank Battles, Triggers, and other topics in Border.

Border Enlistment Arc
Yoneya is mentioned to have been babysitting Yōtarō for her. Later, she appears at the meeting, aiding Replica in his explanation of the Neighborhood.=

Third Neighbor Attack Arc
She is the operator of Tamakoma First during the invasion, giving directions to Karasuma and Osamu so they could reach HQ and battle their opponents.

B-Class Rank Battles Arc
She acts as the operator of Mikumo Unit. She helps them plan for their battle with Arafune Unit and Suwa Unit.