Name: Kei Tachikawa Age: 20 (University student) Height: 180cm Likes: Udon, mochi, croquettes, winning Rank Wars Affiliation: Border HQ, A-Rank #1 Tachikawa Unit Rank: A-Rank Agent, Captain Title: No. 1 Attacker, Overall No. 1 Individual A young man with messy light-colored hair and a goatee. His eyes have a grid-like pattern. Notably, Tachikawa is the only Border agent who uses dual-wielded Kogetsu. He can bisect a Rabbit—which even A-Rank agents struggle with—in a single stroke, and he cut down an Ilgar in self-destruct mode that Ai Kitora couldn't even scratch. In Border, where 10,000 points is considered top-tier, he alone possesses an extraordinary score of over 45,000. Upon his debut, he exuded an aloof, eccentric aura, with Miwa even remarking that his methods resemble Jin's. However, his core motivation is that of a battle junkie, and he is quite hopeless in everything outside of combat (studies and private life), gradually becoming more of a gag character. His passion for mochi is second to none; he was seen stuffing his face with it even during lunch right before the Large-Scale Invasion. His only skill besides fighting is grilling mochi on a charcoal brazier. He is Jin's rival but doesn't hate him; they share a top-tier rivalry based on mutual respect.

Name: Kohei Izumi Age: 17 (High school student) Height: 175cm Likes: Fried shrimp, croquettes, mandarin oranges, All-Range Attacks Affiliation: Border HQ, A-Rank #1 Tachikawa Unit Rank: A-Rank Agent Title: Shooter A Shooter belonging to Tachikawa Unit. A young man characterized by light hair and narrow eyes. He possesses top-class Trion capacity even within Border and is a powerhouse who, along with Tachikawa, keeps the unit at the #1 spot despite having Yuiga on the team. The author calls him a genius. He is in the same class as Yoneya in high school, and they seem to be close friends who call each other "Bullet Idiot" and "Spear Idiot." He also appears to be close with Midorikawa. During the Large-Scale Invasion, the three of them acted together, defeating Lambanein through their coordinated efforts and the help of a B-Rank joint force. He earned a First-Class Merit for this achievement. Since the invasion, he has deepened his friendship with Osamu, a fellow Shooter. While he has been asked to teach Composite Bullets, he is currently waiting for Osamu to gain more combat experience before starting the lessons. He is Ninomiya's mentor.

Name: Takeru Yuiga Age: 16 (High school student) Height: 169cm Likes: High-end French cuisine, being respected Affiliation: Border HQ, A-Rank #1 Tachikawa Unit Rank: A-Rank Agent Title: Gunner A condescending jerk who boasts about being a member of the #1 A-Rank team. He behaves in a pretentious manner, often seen running his fingers through his bangs. He has intense emotional swings and frequently overreacts. To put it bluntly, he's loud. While he is aware that he is weak, he hates losing, making him a very high-maintenance personality. When Izumi suggested to Osamu that he would teach him Composite Bullets if Osamu could win 100 1v1 matches against Yuiga, Yuiga wailed and refused because he knew he would lose 100 times. As soon as he realized Osamu was weaker than him, he reverted to his usual arrogant attitude, acting like a big-shot senior. On the other hand, while Izumi is a "very strict senior," Yuiga ultimately follows orders despite his extreme selfishness, so there is no real conflict. Izumi and the others seem to treat him with cold indifference rather than trying to kick him out, essentially humoring him since he wants to be there.

Name: Yuu Kunichika Age: 18 (High school student) Height: 163cm Likes: Ishikari hot pot, buttered potatoes, all kinds of games Affiliation: Border HQ, A-Rank #1 Tachikawa Unit Rank: A-Rank Agent Title: Operator Border's No. 1 gamer who loves games so much they are a part of her life. She enjoys life in a cycle of eating, sleeping, and gaming. She is a sore loser who cries and gets angry, even jokingly strangling her opponent when she loses a match. The Tachikawa Unit strategy room is filled with a vast collection of old and new consoles she brought in, which the whole team plays. Additionally, a small room in the strategy room serves as her personal nap room for all-night gaming sessions. She is well-endowed; in Volume 13, her chest area was adjusted with screentone, likely by the manager Koma-san. She attends a regular high school, but her academic performance is mediocre, and she, along with Toma, is looked after by their classmate Yuka Kon. In the BBF data, she ranks in the bottom three among females, after Nire and Osano. Despite being a bit of a "disappointing girl," she reached A-Rank #1 alongside Tachikawa, proving that grades aren't everything. Her BBF parameters for equipment operation, information analysis, and parallel processing are among the top for operators, and her total stats are #1. Her equipment operation is particularly high at 10, tied with Usami, likely due to her gaming hobby. Her Trion capacity is 1, but she and Usami are the only characters with such a low value. According to Tachikawa, the crescent moon in the background of the unit emblem represents her. She does her job well, efficiently preparing maps for Izumi during the fight against Lambanein and providing the latest info to Tachikawa, who cares about the New Model kill rankings. During the B-Rank Rank Wars Round 6, she formed the "18-Year-Old Idiot Trio" with Toma and Zoe for commentary, showing surprising intelligence by knowing what inverse proportion is. Her mother is from Hokkaido, and she joined Border about three years ago via out-of-prefecture scouting. Her mother's family sends Ishikari hot pot sets, sea urchin, crab, and salmon roe, which the whole team eats together. The mysterious crab clock in the strategy room might also be a gift from her family.