Fat and weak-willed, he was frequently bullied. His depressed hikkikomori cousin made him question the value of his life, and that of others.
However, after Honda's battle, he non-fatally stabbed the teacher who had used her, with a knife she had given him. He discussed with Captain Tanaka his views on the insignificance of individual human lives and about sacrifices. He wondered if he could muster the courage to fight and kill another human, even knowing the entire world’s fate depended on it, and asked Tanaka to kill him and replace him if he failed. Before his battle started, he showed himself to the opponent robot, and their pilot, a girl, did likewise, revealing many cuts and slits along her arm. This moment finally gave Kirie the resolve to fight. They then returned to their robots and began to battle. The details of his battle were not provided as the next chapter skips ahead, but it is clear he won. His chair was a fancy stool.
In the anime, Kirie lacked the will to fight, but his opponent committed suicide in front of Zearth, ripping out and crushing its own cockpit. Despite this technical win, Kirie did not die and remained the pilot for a second match. Interestingly, Kirie turned out to be a natural at piloting Zearth, quickly and effortlessly overwhelming the enemy robot. After the fight, Kirie confirmed his suspicions about Machi and unveiled her true identity. He then died quietly amidst the commotion as Kanji restrained a furious Anko, who had begun to attack her.
