Kō Murakami/Plot

Background
About 2 years before the January in which Yūma enlisted into Border, Murakami joined Border. Murakami was mentored by Arafune, and the former found himself easily grasping the concepts of battle. 8 months prior to Kuruma Unit's Rank Battle against Nasu Unit and Mikumo Unit, Arafune quit being an Attacker. This upset Murakami, as he believed that his mastery had discouraged Arafune. Arafune assures him that that wasn't the case.

Large-Scale Invasion Arc
He operates alongside Kuruma Unit, which encounters a Rabbit. When his unit goes to join the B-Rank union, he is forced to take care of them himself. He is disadvantaged, but is prepared to put up a fight, when he is saved by Tachikawa.