WARNING: The following contains spoilers for Vol. 2 of The Detective Is Already Dead light novel, now on sale from Yen Press.
The anime adaptation of the popular light novel series The Detective Is Already Dead aka Tantei wa Mou Shindeiru (Tanmoshi) aired its first season in both Japan and the US as part of the summer anime lineup. While the anime adaptation got a mixed reception in the US, it is at least remembered for its seventh episode which depicted a very drunk Siesta -- the series' titular ace detective -- wanting to sleep with her assistant, Kimihiko Kimizuka.
While the anime leaves it rather ambiguous whether or not Siesta actually slept with Kimihiko, the same is not true of the light novel version of that same scene...at least in the Japanese-language version of the source material. Whereas the anime makes a few changes to the way Siesta initiates a sexual encounter to comply with Japanese censorship laws for television broadcast, the light novel depicts Siesta's intentions and Kimihiko's response to Siesta's sexual advances more clearly.
Siesta Fell In Love With Kimihiko At First Sight
One of the major differences between the light novel series and the anime adaptation is that there's a lot more sexual tension built up between Siesta and Kimihiko in the original source material. In fact, the first time a past sexual encounter between them is acknowledged is in Vol. 1 of the light novel series during the fight with Chameleon, a SPES pseudo-human.
In Vol. 1, Siesta (in Nagisa Natsunagi's body) asks Kimihiko to recall what really happened between them the night they both got drunk in London and ended up in bed together. Kimihiko denies having slept with her, but Siesta confirms in the Japanese-language version, "I see. To tell you the truth, at least once, I could consider sleeping with you." This same exchange is featured in the anime version, though Siesta's line is modified to "I see. To tell you the truth, at least once, I wouldn't mind doing it with you."
Vol. 2 follows up on that conversation by building up the circumstances that led to that moment in their past via a flashback storyline. Following their first case involving a plane hijacking, Siesta consistently pestered Kimihiko about becoming her assistant. When asked about why she so badly wants him to work alongside her, Siesta replies, "to tell you the truth, I fell in love with you at first sight." Kimihiko dismisses her response as a joke she thought up at the moment. However, the progression of Vol. 2's storyline suggests she may have actually been telling the truth.
Siesta Is Surprisingly More Sexual Than She Lets On
Most of Siesta and Kimihiko's sexual tension is built up during their investigation of a modern Jack the Ripper case in London. Throughout their interactions, Siesta consistently makes sexual references, many of which hint at her own sexual attraction towards Kimihiko. The major one that foreshadows the eventual consummation of their relationship in Vol. 2 is in the chapter where she sets up a trap for Cerberus, the SPES pseudo-human operating as the modern Jack the Ripper.
When Siesta sets her plan in motion, she sets up Kimihiko as bait for Cerberus in a hotel room. This makes the latter feel unsafe and expresses wanting Siesta in the room with him in order to feel protected. Siesta jokingly reinterprets his words to mean he wants to get in bed with her, which actually hints at what she herself wants from him. Siesta's sexual joke stops being a joke the moment she acts on her true feelings in a state of drunkenness.
The first time Siesta and Kimihiko try alcohol together, they both learn the hard way what happens when their inhibitions are lowered. They both return drunk to Siesta's bedroom wearing nothing but bathrobes, which helps facilitate a late-night mood. At one point, Siesta invites Kimihiko to her bed where she tells him how much she cherishes their time together, making her feel like the conversation has gotten too serious.
When Kimihiko comments that seriousness is all there is to her, Siesta is taken aback by this comment as she doesn't see herself as one-dimensional. This prompts Siesta to draw her body closer to Kimihiko's and utters her famous line of "once in a while, shall we do something frivolous?" ("tamani wa, fumajime na koto, shitemiru?"). Kimihiko becomes sexually aroused when he hears those words and begins to reciprocate Siesta's sexual advances. The chapter in Vol. 2 ends with Kimihiko lying on top of Siesta, initiating sex.
Nigojū Gets Final Say On Siesta And Kimihiko's One-Night Stand
While series author Nigojū doesn't depict Siesta and Kimihiko's bedroom play on the page, he does confirm through the character's reactions in the aftermath that a sexual encounter did take place. Kimihiko in the Japanese-language version of the book describes their encounter as being met with "late-night tension." He immediately panics at the realization his drunken state didn't allow him to forget what he did with Siesta in bed and begins to question his own judgment.
In the Japanese text, Kimihiko further describes their one-night stand as "shameful behavior" (shuutai), which makes him express "I want to die" aloud. This strongly implies he's aware of the lack of clear consent with drunken sexual encounters and is especially fearful of Siesta's reaction when she wakes up and realizes what happened between them. His concerns are immediately validated when Siesta inspects her own body under the covers.
Siesta's subsequent actions make it clear she is far from proud of the one-night stand. Part of the reason for this is obvious: she feels violated due to the fact she wasn't able to consent under the influence. The other reason she's ashamed of the one-night stand is the fact she's not comfortable with the level of vulnerability sexual intimacy entails. The fact Kimihiko got to see this side of her made her feel exposed, which informed her decision to forcibly erase his memories with a modified version of a drug she procured from the Toilet no Hanako-san case. In the light novel, she used her own body weight to pin him on the floor and tried to inject the drug into his arm, but was interrupted by Alicia.
With the aftermath strongly confirming the one-night stand first mentioned in Vol. 1, it then begs the question of why Kimihiko denied having sex with Siesta when she asked him about it. At first, it seems he does so as an act of self-preservation, but author Nigojū offers a different explanation. In an interview with LN News in Japan back in 2020, Nigojū stated, "Kimizuka said there was nothing in Vol. 1. However, he also learned he lost his memory and Kimizuka is an unreliable narrator…only Siesta knows what happened. I'll leave that to the reader's imagination (laughs)."
In context, Nigojū confirms Kimihiko's memories were altered during the battle with Hel in the final chapter of Vol. 2, which takes place after his one-night stand with Siesta. As such, his recollection of the event is unreliable in Vol.1 because a year had passed since that battle. Siesta, however, compiled video footage of their time together in London prior to her death to help restore Kimihiko's memories, which includes the one-night stand. The detail Nigojū is leaving to the reader's imagination is what they actually did during their bedroom play.