Sōya Kazama/Plot

Background
Kazama joined Border during its debut.

Black Trigger Retrieval Arc
Kazama returned to the Mikado City from the mission as a part of the Expedition Force. After reporting the results of the last expedition, he and the rest of the Expedition Force were then informed by Kido that there was a Black Trigger in Tamakoma, which surprised Kazama and Tachikawa. Kido then ordered Miwa Unit to explain the situation: following a hint, they discovered a Neighbor with a Black Trigger. Mr. Kido then explained he joined Border through Tamakoma Branch. After the explanation, Kido tasked the Expedition Force to tag along with Miwa Unit and retrieve the Black Trigger no matter what.

On the way there he and his group were stopped by Jin, who said he wanted to protect his "junior". Arashiyama Unit appeared and teamed up with Jin. He, Utagawa, and Tachikawa went after Jin, while the others stayed behind to fight Arashiyama Unit. When Yūichi used Fūjin, he and Kei were easily defeated by him.

Later he and Tachikawa met with Jin, who talked with him about his decision to give away Fūjin. Kazama was surprised that Yūichi gave up his trigger to protect Yūma.

Border Enlistment Arc
Kazama watched Yūma's fight, because he was interested in him. When he has learned that Yūma was a member of Osamu's Unit, he challenged Mikumo to a mock battle. He easily defeated Osamu 24 rounds, and then revealed that Jin gave away his trigger Fūjin so that Yūma could join Border, saying it was worthless. This prompted Mikumo to ask him for one more round, which he accepted. Taking advantage of the fact there was no trion limit inside the room, Mikumo filled it with slow-moving pellets. He tried to attack Osamu, but Osamu used a Shield trigger to defend himself and then smash him against the wall. He used a Shield trigger to prevent himself from hitting the wall and used Scorpion to stab Osamu's neck, but his left arm was destroyed as a result, rendering him down, which resulted in a draw. Following the battle, he notes that Osamu is weak, but he is nevertheless interested to see where Osamu will go with his intellect. Later, he comments on Yūma's battle with Midorikawa, noting that Yūma had a clear advantage. He is next seen at the meeting regarding the Second Large-Scale Invasion. He does not say anything.

Large-Scale Invasion Arc
After Kōtarō Suwa was captured by a Rabbit, Kazama Unit came to fight it, and Kikuchihara and Utagawa helped Hisato Sasamori and Daichi Tsutsumi (respectively) get up. They fight the Rabbit with difficulty. However, Kikuchihara's Side Effect comes in handy to detect its weak spot and defeat it. After, Enedra comes to the battlefield. They use Kikuchihara's Side Effect to predict where Enedora's sneak attacks would come from. Enedora pretends to go into a rage to lure Kazama, and then gasifies himself and sends gas into Kazama's trion Body, from which he forms blades. Kazama suffers a severe trion depletion and Bails Out. When Kikuchihara and Utagawa prepare to take on Enedora, Kazama urges them to retreat. They follow his orders.

After the invasion with Aftrokator, Kazama visited Omasu where he was hospitalized. He met with Izumi, Midorikawa, Yosuke and asked them not be noisy because they are in the hospital.

B-Rank Rank Battles Arc
During the Tamakoma Second vs. Suwa Unit vs. Arafune Unit battle, Kazama unit watches the match from the operation room. Afterward, Shiori, along with Osamu and Chika, meets Kikuchihara and Utagawa in the hallway, and they tell them that they watched the match and that Kazama commented that using Suwa was a good strategy but it would not work next time. Kazama is also a commentator with Nozomi Kako during the Tamakoma Second vs. Ninomiya Unit vs. Kageura Unit vs. Azuma Unit battle. At the start of the match, Kazama comments that the unconventional map and weather was unexpected, then suggests that Ninomiya Unit was being cautious because they were trying to figure out what Azuma Unit was planning. For the rest of the match, he mainly comments on Osamu's role and defeat.

With Tachikawa, Konami and Murakami, Kazama is sent to intercept the two intruders sent to destroy the ship during Galopoula blitz. He attacks Gatlin while invisible, managing to cut off his arm. He later fights against Ratarikov, managing to defeat him borrowing Kuga's strategy of using his own severed arm as a diversion.