The Case of Chiaki Yoshino Chapter 01 of Volume 01 (吉野千秋の場合, Yoshino Chiaki no Baai) is the first chapter of the Sekai-ichi Hatsukoi light novel series. It begins the story The Case of Chiaki Yoshino that follows Chiaki Yoshino and his developing relationship with Yoshiyuki Hatori and the love triangle formed with Chiaki's close friend Yuu Yanase.
The chapter was the debut of the Sekai-ichi Hatsukoi series, along with The Case of Ritsu Onodera No.1 which was published in the same issue of The Ruby magazine.
The chapter opens with Chiaki and Hatori sitting in a diner. Hatori reviewed Chiaki's storyboard, and having disliked it, tossed it down and accused him being arrogant and thinking 'anything' would pass since Chiaki is a popular manga author. Irritated by the accusation, Chiaki made attempts at defending himself, quickly being shot down by Hatori who demanded he do the storyboard over again.
Chiaki soon after reflects on his friendship with Hatori, who is also his editor. The two had been together almost since birth, having grown up together and lived in same neighborhood. Despite the occasional bickering between the two, Chiaki can't imagine being separated from Hatori.
Later on, Hatori invites Chiaki to view a firework display near a riverbank with him. Chiaki, having wanted to use fireworks in his next story, eagerly agrees while talking about wanting a caramel apple.
The two return to Chiaki's apartment, where Hatori prepares dinner for the two of them. As Chiaki praises Hatori's cooking skills, he also questions why Hatori doesn't have a girlfriend yet. Hatori then explains that he has somebody he likes, but he doesn't feel as though pursuing the relationship with this person will benefit him at all. Despite pushing for information on who this person that Hatori likes is, Chiaki is unable to figure it out. The battery of questions pushes Hatori to admit that he wouldn't have any time to date anyway because his work keeps him very busy. He also notes that Chiaki is the worst author he has when it comes to making his deadlines. Although Chiaki tries to refute this, he fails once more and instead, apologizes. As Hatori elaborates a little more on his crush without dispelling any truly useful information, the door bell rings.
Chiaki's other friend and assistant, Yuu Yanase, makes his first appearance at this point. Letting himself in after Chiaki unlocks the door, he hands over a gift for Chiaki, a limited edition manga he hadn't been able to pre-order and assumed he had just missed. A tense atmosphere fills the room as Yuu and Hatori lay eyes on each other, followed by Yuu teasing Chiaki for having Hatori do so many chores for him such as making his dinner.
Chiaki, thinking deeply on what Yuu has said about his dependency on Hatori, wonders to himself if it bothers Hatori that he's so hopeless. Chiaki once again wonders who this 'mystery woman' Hatori likes is, and what sort of woman she is.
Later, Chiaki hands in his storyboard directly to Takano of the Emerald editing department. He had mentioned to Takano his plans of visiting a nearby art store while he was out since he was low on supplies, to which Takano urges him to hurry as rain is in the forecast. Just as Chiaki gets outside, it begins pouring. While seeking a place to take shelter from the rain, Chiaki notices Hatori and Yuu. The force of the rain drowned out Chiaki's initial call to Hatori, before he can call out again, he witnesses what he believes to be the two in a 'lovers position'. Stunned, he hides behind a vending machine before either of the two notice him, internally realizing that the 'mystery woman' Hatori spoke of, must've been Yuu. Confused about this, he reminds himself not to think badly of them because 'it's not good to have a prejudice'.
Although shocked by the situation, Chiaki comes to terms with the newly discovered relationship between his childhood friend and Yuu.
summary in progress
The chapter has been adapted into the drama CD series and the anime series.
The anime series tones down explicit content, and most notably the rape is removed. The anime has Hatori only kiss Chiaki and move his hand up his shirt before fading out, and nothing further is really suggested. Their later sex scene in the bathroom is completely replaced with them making out on the bed, fading out as they kiss.