Osamu Mikumo A brilliant leader. While his individual combat power is low, he always gets the job done in team battles. 15 years old. He serves as the captain of Tamakoma-2 (Mikumo Unit), a B-rank Border squad. To save Chika's friend and brother who were taken by Neighbors, he aims to join the expedition force to the Neighborhood along with Yuma and Chika. Although his lack of experience in combat is noticeable, he fights hard, compensating with a flexible imagination that others describe as "doing whatever it takes." Follow the official setting guide for further details.

Yuma Kuga A boy from the Neighborhood. Despite his youthful appearance, he is 15 years old, the same as Osamu. Invited by Osamu, he formed Mikumo Unit with Chika Amatori. His attacks, which utilize his extensive combat experience and agility, are among the best in Border. He possesses a Side Effect that allows him to see through lies. He holds a Black Trigger, a memento from his father, Yugo Kuga. Follow the official setting guide for further details.

Chika Amatori 14 years old. Osamu's childhood friend. Because she possesses a massive amount of Trion, she has been targeted by Neighbors since she was young. To rescue her brother and friend who were taken to the Neighborhood, she joined Border and formed Mikumo Unit with Osamu and Yuma, aiming for the expedition force. Despite being a Sniper, she has a weakness: she cannot shoot people. Therefore, she uses Lead Bullets (Red Bullet). Follow the official setting guide for further details.

Hyuse A Neighbor from the military nation of Aftokrator. He assaulted Mikado City during the large-scale invasion. He faced off against Jin but was abandoned by Hairein and left behind in this world. Currently, he is being held at the Tamakoma Branch as a Border prisoner. He joined Tamakoma-2 on the condition that he be returned to his home country, Aftokrator. Follow the official setting guide for further details.

Shiori Usami An operator at the Tamakoma Branch. She serves as the operator for both Tamakoma-1 and Tamakoma-2. She also plays an active role outside of combat, such as analyzing Neighborhood technology. Follow the official setting guide for further details.

Yuichi Jin A carefree young man belonging to the Tamakoma Branch. He possesses top-tier combat power within Border and calls himself a "talented elite." He is a veteran member who has been with Border since its early days. He was formerly an S-rank agent who held the Black Trigger "Fujin," a memento of his mentor Soichi Mogami, but he gave it up in exchange for Yuma's admission into Border. He has a precognition Side Effect that allows him to see a bit into the future of people he sees.

Kyosuke Karasuma Follow the official setting guide.

Kirie Konami Follow the official setting guide.

Reiji Kizaki Follow the official setting guide.