Masamune Kido/Plot

Past
Kido was a member of Old Border with Shinoda, Rindō, and Yūgo. He was senior to the former two and colleague with the latter. He was initially a cheerful person who believed that Earth and the Neighborhood could be united, but after the deaths of several of his colleagues in a war with a country in the Neighborhood. Yuri claims he abandoned that view and became pessimistic about any unity between Earth and Neighbors however this might not be fully true as he allowed Yūma and Hyuse to join border when he could of rejected them both then even went so far as to say he would protect Yūma as long as he followed Border's rules.

Introduction Arc
Kido is first seen at the meeting where Osamu's punishment would be decided. During the meeting, the topic of irregular gates is also discussed. Osamu is not punished since his actions have raised Border's reputation. After Osamu leaves, he allows Miwa to monitor him since Miwa suspected that he was hiding a Neighbor, and eliminate it if there really was one.

Black Trigger Capture Arc
After Miwa Squad discovers Yūma, he has Osamu questioned. After learning more about Yūma, he orders Jin to steal his Black Trigger. When Jin refuses, he orders Rindō to order Jin. Osamu reveals the surname of the Neighbor, Kuga, which surprises Kido as well as Shinoda and Rindō. Shinoda reveals that the Kuga they knew, Yūgo Kuga, was a founding member of Border and Kido's colleague. In spite of this revelation, Kido is adamant about recovering the Trigger. When the top three teams return from Menoeides, he orders them to capture the Black Trigger, but allows them to choose their methods. After Jin interferes with the mission, he threatens to use Amō should Shinoda get involved. Jin comes in and asks Kido to allow Yūma to peacefully enlist into Border. He dismisses it, calling it a ridiculous request. However, when Jin offers Fūjin as a bargaining chip, he questions Jin's motives. Jin simply states that he wanted to allow his junior to enter Border, and that one day he would be useful to Kido's "true objective." Kido agrees and allows Yūma to enlist.

Border Enlistment Arc
After Yūma makes his debut by defeating the Kōda Squad with ease, and Chika makes her debut by making a hole in HQ's wall, Kido questions Rindō's objective. Rindō assures Kido that he wasn't trying to amass power, but rather, wanted to give them a chance to form a unit and complete their goal of recovering Chika's brother and Harukawa. Kido calls the idea "childish" stating that it was unrealistic due to the size of the Neighborhood, and the general difficulty of life. He is even more concerned about Yūma after Kazama slated him to win against Midorikawa.

He is at the meeting regarding the predicted large-scale invasion. He asks Yūma for information, stating that it was an obligation since he was part of Border. Yūma gets Replica to give the information. Replica first asks for Kido to promise that Yūma would not be harmed. Kido promises, as long as Yūma follows rules. As Yūma does not sense any lies, Replica explains. He is amazed at the map that Yūgo compiled during his time in the Neighborhood. When Replica mentions Liberi, Leoforio, Chion, and Aftokrator as possible invading countries, Kido asks if one was going to participate or more. Replica replies that it was unsure, since an errant nation could also invade (one that did not have a specific orbital path). When Yūma narrows down the possible attackers to Chion and Aftokrator, Kido asks for information on their military power, including Black Triggers. He is shocked to hear that Aftokrator has 13.

Large-Scale Invasion Arc
He allows Yūma to use his Black Trigger provided that he stays within the Danger Zone to avoid widespread panic. During the post-invasion interview, he authorizes the usage of Osamu as a scapegoat, but later comes to Osamu's defense, criticizing a reporter.

B-Rank Wars Arc
Before Tamakoma Second's first rank battle, he meets Osamu, wishing him luck. Osamu forgives him for using him as a scapegoat, but warns Kido to never do the same to Yūma or Chika.