Ai Kitora/Plot

Background
When she was in B-Class, she rose through the ranks as a Gunner, but started using Scorpion because bullets were too Trion-consuming, especially with her low Trion. When she was still in high school, she became an A-Class member of Border. She was trained by Karasuma in the past, just like Osamu is now.

Introduction Arc
She first appears with Arashiyama, responding to an attack on the school. Upon learning that Osamu had breached the rules, she scolded Arashiyama for praising Mikumo and berated Mikumo in turn. Yūma contradicted her by questioning her line of reasoning, saying that Triggers were originally Neighbor's technology. She became embarassed, and this deepened as Yūma continued on with how she merely being spiteful.

Kitora, later on, was sent to 'escort' Osamu to Border HQ, stating that she was there merely to ensure Osamu doesn't run. However, on the way there, a neighbor appears and starts attacking the civilians. In response, she activates her Trigger and goes after it. After she analyzed the Ilgar's path, she climb on top of it by jumping off a bridge and reels herself in by using her Spider. However, as soon as she landed, the Ilgar activates its countermeasure. In the nick of time, Kitora manages to protect herself by activating Shield. She then retaliates by cutting off a piece of its armor and shooting the exposed part. By doing so, the Ilgar activates its self-destruct protocol and starts heading towards the city. She tries to stop it by shooting it but to no avail. At that moment, Yūma assists her by hooking Chain to its underside and pulling it into the river, just in time before it explodes. After she pulls herself out of the river, Kitora questions about what just happened and her inability to stop the Ilgar. At that moment, she sees Osamu being surrounded by a crowd who thank him for his efforts. This leads Kitora into thinking that Osamu actually wants to be popular. However, this turns out to be false when Osamu tells the crowd that she was actually the one who saved them. As she corrects her judgment, Yūma congratulates her on her success in bringing down the Ilgar. But, she states that it was someone else who did it and she didn't do anything noteworthy. She then goes on to deal with the crowd who are unsatisfied with Border's failure to protect them.