Just as Ishigami has received an unexpected visitor, Yukawa, in the previous chapter, so does Yasuko receive an unexpected visitor of her own, a former regular at Club Marian named Kudo. The two unexpected visitors, prompted by concern for their counterparts after hearing about the police investigation, enter the story at the same time: Kudo appearing in Yasuko's life out of concern for her well-being and Yukawa appearing in Ishigami's life after many years being out of touch. These unexpected visitors also highlight the irrevocable changes that have occurred in the lives of Yusako and Ishigami: just as Ishigami can't enjoy what would otherwise have been a fruitful friendship with Yukawa, so Yasuko may not be able to enjoy what otherwise might have been a new beginning with Kudo, as it might trigger feelings of jealousy in Ishigami.

Kudo represents an ideal partner for Yasuko, which will force the reader to entertain doubts about Ishigami's status as worthy protagnoist. Unlike Togashi, Kudo is gentle and compassionate, always responsive to Yasuko's needs and never blaming her or passing judgment on her. Togashi, by contrast, had always been quick to blame and judge Yasuko. Unlike Ishigami, Kudo is socially well-adjusted and understanding of people's feelings, having been married before. While talking with Yusako, Kudo does not say anything to disparage his wife. He takes blame for the fact that Yusako might have to get soaked in the rain. He takes the initiative to hail a cab to take her home. He asks her for dinner, even offering to take Misato along. As a foil for Ishigami, Kudo's presence in the the story casts doubt on the sincerity of Ishigami's motives. When it was only Ishigami and Togashi who were the two men in Yasuko's life, it was clear which one was the better choice for Yasuko. With Kudo now in the picture, it is less certain whether or not Ishigami is such a heroic figure after all. Just as Yukawa's presence proves that genius, social awareness, and emotion are not mutually exclusive, so does Kudo's presence prove that love for Yusako need not be expressed via a complex plan to rescue her from a difficult predicament.

While Ishigami is careful to get rid of Yukawa before the latter could see him walk into the lunch box shop, Yusako is not so careful about preventing anyone from seeing her with Kudo. When Ishigami makes his usual call to Yusako, he wavers and hesitates, restraining the urge to ask specifically about Kudo, which makes Yasuko uneasy. While Kudo doesn't threaten any aspect of Ishigami's plan, it induces feelings of insecurity and jealousy in Ishigami, which will prove to be a weakness that undermines his plans and causes him to fall under suspicion. Apparently, basic human emotions like carnal desire and jealousy have confounded the strictly logical and mathematical approach that Ishigami hoped would be Yasuko's salvation. This creates suspense centering on the internal state of both Ishigami and Yusako. Kudo's presence in Yusako's life as a foil for Ishigami will create tension in her life since she will feel torn by her gratitude to Ishigami on the one hand and her desire to start anew with Kudo on the other. It will also create tension for Ishigami, as he must balance his strictly logical approach to the murder case with feelings of insecurity triggered by Kudo