Sōya Kazama/Plot

Black Trigger Retrieval Arc
Sōya returned to the Mikado City from the mission as a part of Expedition Force. After reporting the results of the last expedition, he and the rest of the Expedition Force were then informed by Masamune Kido that there was a Black Trigger in Tamakoma, which surprised Sōya and Kei. 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 explaination, 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 Yūichi, who said he wanted to protect his "junior". Arashiyama Unit appeared and teamed up with Jin. He, Ryō and Kei 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 Kei met with Yūichi, who talked with him about his decision to give away Fūjin. Sōya was suprised that Yūichi gave up his trigger to protect Yūma Kuga.

Rank Wars Arc
Sōya 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 20 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 againt 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.

Third Neighbor Attack Arc
After Kōtarō Suwa was captured by a Rabbit, Kazama Unit came to fight it, and Shirō and Ryō helped Hisato Sasamori and Daichi Tsutsumi (respectively) get up.