The Detective Is Already Dead spent several episodes detailing Kimihiko Kimizuka's last case with Siesta leading up to the latter's death. In those episodes, viewers were treated to more of Kimihiko and Siesta's fun dynamic as they investigated SPES activities in London, England. Siesta even revealed her more vulnerable side when she and Kimihiko drank alcohol for the first time, leading up to a not-so-fondly remembered night together in Siesta's bed. All this buildup crushed viewers' hearts when the moment came to reveal what truly happened to Siesta on the fateful day she lost her life in Episode 9.

Picking up where Episode 8 left off, Siesta, Kimihiko and Charlotte Arisaka Anderson (aka Charl) were on a boat making their way to an island to defeat Hel and recover Alicia. The latter was actually one of Hel's Dissociative Identity Disorder alter egos. Charl and Kimihiko went to the SPES base to fight Chameleon, who turned out to be an extraterrestrial plant known as SEED, the true leader of SPES. SEED's true objective was to terraform the Earth and reproduce, killing every living thing in the process. While Charl fended him off, Kimihiko went to assist Siesta in her battle with Hel.

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The Implications of Nagisa Natsunagi's True Identity

During their fight, Hel revealed to Siesta that Alicia was the real personality. Sometime after SEED arrived on Earth, he abducted Alicia and carried out torturous experiments on her body, traumatizing her. This in turn caused Alicia to develop the non-binary Hel personality, presumably to protect herself from the horrors she experienced. Hel, however, chose to embrace SEED's villainous mission and tortured Alicia themselves. Siesta deduced that Hel was actually driven by a need for love from a father figure, which angers them, validating Siesta's deduction. The fight, however, turned deadly when a monster Hel previously controlled ran loose, resulting in Siesta losing consciousness and Hel killing the monster. This wore out Hel's transplanted heart, and they proceeded to replace it with the heart of the unconscious Siesta, killing her in the process.

This reveal in The Detective Is Already Dead did a lot more than show the events that resulted in Siesta's death. It actually had significant implications as to the true identity of Nagisa Natsunagi, the host of Siesta's heart. In fact, the episode seemed to confirm that Hel and Nagisa were one and the same. To start with, they have a similar appearance, with Nagisa looking like Hel with longer hair. Nagisa also demonstrated that she had gaps in her memory (such as not remembering who her heart donor was), which is a symptom of Dissociative Identity Disorder.

Furthermore, the Nagisa personality may have been born out of both Siesta's and Alicia's personalities, as she had traits of both. The final touch was the red ribbon Nagisa wore in her hair -- the same ribbon Siesta wore during the Toilet no Hanako-san case, and it's the same one she promised to give to Alicia in London.

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The Impact of Siesta's Death on Nagisa and Kimihiko's Relationship

The last thing that's significant about The Detective Is Already Dead's flashback story arc's conclusion is that it proved to be an important episode for both Siesta and Kimihiko. Since the start of the episode, Siesta consistently hinted that she knew she was going to die and tried to say goodbye to Kimihiko the only way she knew how. Prior to the fight with Hel, Siesta wanted to hug Kimihiko, but he declined. She also wanted to tell him how she truly felt about him, but he refused to hear her out. It's not until Hel succeeded at killing Siesta that Kimihiko finally broke down and admitted that he'd always loved Siesta and regretted not expressing this when he had the chance.

In many ways, Episode 9 was always going to be a heartbreaking episode to watch. Not only did it finally reveal how Siesta truly died, but it also validated the romantic attraction that always existed between her and Kimihiko, making her death all the more devastating. With the revelation that Hel and Nagisa might be one and the same, the reality of this gravely impacted Nagisa's relationship with Kimihiko moving forward, especially given Kimihiko's own feelings for Siesta.