Kotarō Tomoe/Plot

Background
Three months after Border moved to its publicly known HQ, Tomoe saw Kuniharu Kakizaki on television and thought he was cool. He enlisted about two years later, which caused him to become the first elementary schooler to join Border. He jumped at the chance when he discovered that Kakizaki was creating his own Squad and applied immediately.

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

Large-Scale Invasion Arc
Along with the rest of his Squad, Tomoe joins the fight against Ranbanein. The Neighbor forces them into hiding until Kōhei Izumi, Shun Midorikawa and Yōsuke Yoneya join the fight. At Haruaki Azuma's command, the members of Kakizaki Squad start firing at Ranbanein to pressure him into revealing openings. When the Neigbor targets Tatsuya Kuruma and anticipates Yoneya's ambush, Tomoe, along with Kuruma, Midorikawa and Tsuneyuki Okudera casts his Shields in front of the Attacker, allowing him to close the gap and defeating Ranbanein. Kakizaki Squad is subsequently deployed to defend the southern area of the city. To the best of Tokieda's knowledge, it was the only B-rank Squad to survive Aftokrator's invasion without a single bail out. It was also the recipient of an Excellent Distinguished Service award.

Round Two
On February 5 Kakizaki Squad fights a rank war against Suzunari First, Urushima Squad and Nasu Squad. They score two points, but it is Kō Murakami who earns the survival bonus.

Round Three
Kakizaki Squad drops to the bottom group of B-rank after losing to Arafune Squad.

Round Four
After the fourth round, Kakizaki Squad climbs back to the middle group of B-rank.

Round Five (Night)
On February 19, the day of the match against Tamakoma Second and Katori Squad, Kakizaki has his teammates learn all the building locations of their map of choice and warns them against fighting Yūma or Katori if the three of them are not together. They laugh when he answers Ui's question about his impression of Yūma by saying that he seems a nice guy. Tomoe is amazed by Tamakoma Second's resolve to make the next away expedition despite having only recently joined Border. The three fighters agree to meet up before engaging any opponent when they spawn, and they do so, ignoring the clash between the two enemy aces. Kakizaki Squad waits for Katori Squad to leave Tamakoma Second wire zones and immediately engages them in a firefight, with Tomoe attacking Yūta Miura to disrupt their formation. The flanking maneuver is successful and Katori Squad is pushed back. However, Kakizaki Squad is forced to retreat when they are lured into a position between the opposing teams. Kakizaki Squad and Katori Squad both decide to fight each other and lure Tamakoma Second out of the wire zone, but just then Chika starts destroying buildings with Ibis.

Kakizaki lets Katori Squad swarm the Spider nest first, since that makes it more likely that they will be targeted by Yūma; however, he is the one who comes to intercept them. The three manage to drive Yūma to an open area, but Yūma stays close to Kakizaki, preventing Teruya and Tomoe from shooting at him, until they switch to their Attacker Triggers, at which point he steps away again. Kakizaki and Tomoe begin cutting the wires, but then Tomoe attempts to pin Yūma in place; however, he is propelled into the air, where Chika hits his arm with Lead Bullet. Pinned to the ground, Tomoebecomes the first to bail out, beheaded by Yūma. He apologizes to Ui, but she responds that there was nothing that he could have done.

After the end of the match, Kakizaki apologizes to his teammates for being overly cautious and not letting them do as they suggested, but Tomoe objects that if they had charged recklessly, they would have been stopped by the wires and Lead Bullet. Together the members of Kakizaki Squad decide to create two-to-one tactics to complement their captain's signature three-man formation.

During the next enlistment day, Tomoe and Miura hear about a newcomer who made B-rank in less than a day. Noboru Koarai is excited at the idea of fighting him, but Tomoe points out that he still has only one Trigger. Tomoe, Miura, Koarai, and Hisato Sasamori propose to fight five rounds against Hyuse each using only their Kogetsu, and he accepts. Tomoe is the second to fight. He loses all five rounds and is amazed by Hyuse's skill, even more so when he bests Shinnosuke Tsuji. When Hyuse duels Tatsuhito Ikoma, Tomoe and Tsuji bet that Hyuse will win, since Ikoma cannot use Senkū, and together with the others watch the match with bated breath. When it ends, Tomoe joins the throng of Attackers in congratulating Hyuse.

Round Eight
On the night of March 5, Kakizaki Squad gathers to spectate Tamakoma Second's match against Ninomiya Squad, Ikoma Squad and Yuba Squad. Tomoe reacts with surprise when Chika protects Yūma and herself against her own Meteor with a Fixed Shield.