• As Ishigami sits in front of his computer, reviewing the photos he had taken of Kudo and Yasuko, the reader is tempted to conclude that Ishigami intends to use the photos for the purposes of blackmail. It may be his way of gaining leverage over Yasuko, whom he hopes to possess for himself, using his knowledge of Togashi's murder like a Sword of Damocles over her head.

• Ishigami imagined the worst-case scenario. He'd need these photos then, for sure. He just hoped it never came to that. While the "worst-case scenario" is not explained in detail, it is tempting to assume that Ishigami hopes to use the secret photos for his own selfish purposes, namely in keeping Kudo from getting close to Yasuko. This is reinforced by Ishigami's observation that Kudo and Yasuko had only met in the hotel for a short time, not long enough for a more sensual tryst:

• Yasuko and Kudo hadn't been together very long. He couldn't help but note of how that fact put him at ease. Ishigami's insecurity is on full display as he simmers with rage at the idea of other people making fun of his romantic interest in Yasuko. It is Sayoko who noted Ishigami's interest in Yasuko, which Sayoko, in turn, told to Kudo and later the police. Having been questioned by the police, Kudo divulged how it had been common for many people, not mentioning Ishigami specifically, had gone to the lunch shop with the aim of seeing Yasuko. After talking to Sayoko at the lunch box shop, Kusanagi confirms that Ishigami, in particular, had a habit of visiting the lunch box shop as an excuse for seeing Yasuko. The realization that his crush for Yasuko, expressed so awkwardly, would make him the butt of other people's jokes, makes Ishigami seethe with anger:

Still, it made his entire body hot with shame to think that someone else, a third party, had noticed first. How they must have laughed to see an ugle man like him head over heels for a beautiful woman like her.

• No longer is usual calm self, Ishigami gives signs of growing emotional instability. This helps build up the sense that the arc of Ishigami's character development is heading towards an inflecion point where he will snap and resort to extreme behavior driven by jealousy and a wounded ego. The motive exists for such extreme action. The ability exists, given Ishigami's tremendous genius. It's only a question of what kind of circumstance is needed to reach Ishigami's breaking point.

• Somewhat indicative of this is Ishigami's assessment of Yasuko as someone who wouldn't be good at mathematics:

What was making Ishigami angry was the roundabout way she was giving him the information. She would be no good at mathematics, he could tell.

• Yasuko's "roundabout" manner, alluded to in the quote above, is the result of her trying hide the role of Kudo in her life. His judgment of her as someone who wouldn't be good at mathematics, while innocent enough, has somewhat of a perversely judgmental quality. It is the first time that he expresses frustration and displeasure with Yasuko, which only enhances the sense that he may be mentally preparing to attempt to blackmail Kudo.

• This demonstrates how the author misleads us in the same way that Ishigami has misled the police. In many ways, Ishigami is a proxy for the author. Just as Ishigami distracts attention from what really happened to Togashi, the author also must distract the reader's attention from Ishigami's true intentions. Keigo Higashino is very much engaged in a cover-up on a different level - that of preventing the reader from determining the full truth of Ishigami's cover-up as well as Ishigami's intentions with regard to Kudo and Yasuko.

• At the same time, we are given hints of a back-up plan that is waiting to be put into action. This occurs specifically when Ishigami instructs Misato to inform the detectives that she had talked with Haruka Tamaoka, another friend of hers, around noon on March 10 about her plans to see a movie with Yasuko that very same day. This has the effect of buttressing Yasuko's alibi, which only contributes to Yasuko's security in the face of increased police scrutiny. This naturally creates cognitive dissonance and suspense in the mind of the reader: if Ishigami is reaching his breaking point as a result of increased frustration over Yusako's relationship with Kudo, why is he now instructing Misato to help strengthen Yasuko's alibi?

• Yukawa is seen in this chapter performing another experiement when Kusanagi comes to visit him. He's ostensibly busy burning papers in an oil drum because it's more effective than using a shredder. An oil drum, however, is what was used to burn the victim's clothes during the murder. Therefore, it is highly likely that Yukawa is performing an experiment that will help him gain more insight into Ishigami's cover-up.

• Science experiments occur frequently throughout the novel. They occur as symbols for the empirical approach that Yukawa relies upon to solve murder mysteries. Experiments are for Yukawa what math problems are for Ishigami. Just as Ishigami's apartment is littered with math books and his desk drawers filled with his own notes on various math problems, Yukawa's lab is strewn with lab equipment used for different kinds of tests and experiments. Just as Ishigami has students whom he guides, instructs, and assesses with math exams, so Yukawa has graduate students whom he also guides and asssesses.

• Upon seeing Kusanagi, Yukawa remarks, "It seems I have stalker." The stalker figure is a recurring motif in the novel. When we are first introduced to Kusanagi and Yukawa, Kusanagi remarks how he's just finished a "stalker" case. Kusanagi has been acting as a stalker himself, shadowing and tailing Kudo, Yukawa, and Ishigami. In Kusanagi's case, acting like a stalker seems justified because he's a detective and is just doing his job. Kusanagi's type of stalking would likely be justified by appeals to the interests of public security, but his methods raise serious questions about the ethics of his approach. He has used misleading and forceful questioning to bully Kudo, lied in order to enter Yukawa's campus, gone behind Yukawa's back by talking to graduate students in order to get information about Yukawa's whereabouts, in addition to putting Yasuko under surveillance. This highlights the double standard and absurdity that results from characterizing Ishigami as a stalker later on.

• Kusanagi shares more theories about how Ishigami could've collaborated with Yusako to carry out Togashi's murder. Yukawa listens attentively but doesn't affirm any of Kusanagi's conjectures. Nor does he explain more about his own theories as to what happened. It is only when Kusanagi at one point mistakenly assumes Ishigami is a "novice murderer," that Yukawa cautions Kusanagi about making such false assumptions: "Murder probably even comes easier to him," says Yukawa of Ishigami, which is a strange remark coming from a friend who cares deeply about Ishigami and wishes to protect him.

• This serves to heighten the tension around Ishigami's growing instability and frustration, making the reader wonder what sort of extreme actions Ishigami is capable of.