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Kazunao Yamada (Japanese: 山田 一直, Romanized: Yamada Kazunao) is Katsuhira's chemistry teacher for Class 2-A. He is a very carefree teacher.
Yamada has long wavy green hair that is slicked back except for two strands that lie down near his neck. He wears a sleeping mask on top of his head along with a wine red track suit, a black shirt, and a pair of crocs. He appears to be 180 cm.
Kazunao takes no interest in the personal lives of his students and is very apathetic. He has no motivation to work hard and only shows interest in Bishoujo style games and cheap food. He also enjoys teasing his students. As shown in episode 5, he caught Maki and Yuta by recording them on his Smartphone. He was likely aware of their conversation based on how long his phone had been recording. And in episode 6, he left a message for the kids asking them to clean up the mess they had left behind in camp. He is shown to not care too much about his student's health, as he watches the Kiznaivers in episode 9 break down emotionally but does nothing to stop this. Mutsumi Urushibara describes this as 'bad taste'.
Yamada is part of the Kizna community and works alongside Urushibara and Sonozaki to monitor the new Kiznaivers. Throughout the anime, he is seen conducting experiments on the Kiznaivers with the help of Urushibara in order to keep bringing out official results to present. At the same time, however, he does not seem as motivated in the experiment as much as Urushibara and Sonozaki are. During a conversation between the three of them, Sonozaki states that she will make sure the Kiznaiver experiment proceeds no matter what, but Yamada disagrees and casually says that if funding for them stops, there's not much they can do. In episode 9, he is seen pushing the experiment on the Kiznaivers to the point of emotional breakdowns without remorse, stating that this is what Sonozaki wants, but Urushibara is angered by this and stops him before it can be taken any further.
The two seem to know each other well and are partners who monitor the Kiznaivers closely. Yamada seems to be comfortable with her to the point where he simply calls her 'Urushii', but as displayed in episode 9, there is some tension between them. Yamada isn't worried about how far is too far when conducting experiments on the Kiznaivers, but Urushibara refuses to push it as far as it can possibly go. Yamada almost threatens her when she attempts to stop him and the experiment, however he is ultimately stopped when Urushibara kicks him in his private area. While the two are colleagues, they do not see eye-to-eye on how the Kiznaivers should be treated.
Their relationship is not strong, but he does work alongside her. They talk very little to each other and when they do it's only for professional purposes, but it does seem like he knows more about her than others. During episode 8, he is surprised when he finds out that Sonozaki understands more about love than he had originally believed, implying that he has been with her for a while. However, he does not display a close relationship with her, and when Urushibara worries about Sonozaki, Yamada calls Urushibara a 'overprotective parent'.
Though not shown directly, it is revealed in episode 10 that Yamada was one of the people that watched over the children that were experimented on, including Katsuhira. Strangely, even though Yamada took care of Katsuhira as a child, the two of them act like complete strangers to each other.