Originally intended to be released in 2003 under the name JoJo's Bizarre Adventure: The Anatomy Lesson of Dr. Nicolaes Tulp following the release of a 31 page draft, the story faced a long and troubled development as Otsuichi was repeatedly dissatisfied with the final result, throwing several full manuscripts until he was finally satisfied. This final product however was very different from the draft originally released to the public.
The story is set in Morioh, the town serving as the set of the series' fourth part; Diamond is Unbreakable, and during the winter of the year 2000. A few days after the New Year, Koichi Hirose and Rohan Kishibe stumble upon a cat drenched in blood, which leads them to a woman who seems to have had a car accident while indoors, without any trace of a car. The heroes of Morioh have to conclude that another evil Stand user is in town. The culprit is Takuma Hasumi, another high-school student, whose tragic and mysterious past is explored as he develops a relationship with Chiho Futaba. Takuma must then avoid being caught by the heroes, while reaching his unknown goals in the process.
The Book: 4th Another Day provides examples of the following tropes:
- And I Must Scream: Akari Hirai is trapped in the space between two buildings, which is so narrow she can't even stretch her arms out. Because of a fence and another building blocking the sides, plus Teruhiko's Stand making everyone not notice Akari, she spends several months in here with nothing to do and the only thing that kept her sanity intact was the hope of escaping it.
- Archnemesis Dad: Takuma deeply hates his biological father Teruhiko for leaving his mother Akari to die between two buildings, so he spends several years plotting his revenge against him.
- Babies Ever After: In the epilogue, Chiho reveals that she is pregnant with Takuma's child, whom she is planning to give birth to.
- Best Served Cold: Takuma's revenge against Teruhiko and his accomplice Hanae takes years of investigation and seduction of Chiho to come to fruition. Takuma has planned his every move so it hurts Teruhiko as much as possible.
- Birthmark of Destiny: Takuma and his father Teruhiko share a horse-shaped mark on their shoulders, and Takuma's mark is a birthmark while Teruhiko's was obtained because an Arrow cut him.
- Bitch in Sheep's Clothing: When Akari had met Teruhiko, he looked like a genuinely good-natured architect who wanted to help Morioh develop. Soon after, Akari discovers that Teruhiko has swindled millions of yen from his projects, and was murdered for this discovery.
- Blade Enthusiast: Takuma always carries several knives with him. They serve as a means to attack people outside of his Stand's range, and a way to quickly defend himself as The Book is not easy to use.
- Blessed with Suck: Takuma has an eidetic memory, but that doesn't mean he's a genius. It means that he cannot forget any bad blood between him and his former friends, and he cannot concentrate on anything because of a constant flow of memories resurfacing. It was so bad Takuma attempted suicide several times and only the apparition of The Book calmed his mind.
- Brother–Sister Incest: Takuma and Chiho develop a relationship, and Chiho even becomes pregnant with Takuma's child. However, Chiho didn't know their blood relation until she was pregnant, and Takuma was purposefuly seducing her despite his disgust, all to take his revenge.
- Call-Back: Several events from Diamond is Unbreakable are mentioned, which have transformed into local urban legends. Chiho, for instance, looks for a whispering book; the same legend is mentioned at the end of the Enigma arc where Josuke is said to have given a book, in reality Terunosuke Miyamoto mixed with paper, to a library. Josuke's mysterious backstory is also heavily focused on.
- Driven to Suicide: Several times Takuma attempts suicide, first because of his eidetic memory which The Book thankfully permitted him to control, and finally after Josuke defeats him and he doesn't have anything to live for anymore.
- Even Evil Has Loved Ones: Teruhiko is a horrible person, but he genuinely adores his daughter Chiho. Takuma targets her precisely because it will hurt Teruhiko the most.
- Heart Is an Awesome Power: Once again, a seemingly harmless Stand is used with imagination to surprising and lethal effects. The Book is a record of Takuma's life and can make people relive Takuma's memories. However, he can use it on himself to learn any skill like knife throwing at an accelerated pace, and then Takuma can make people relive the time he was hit by a car or when he fell from several stories, without the memory of him being treated by doctors, then he can even kill them in one move. Case in point, Takuma manages to beat Okuyasu and nearly defeats Josuke despite his Stand being a simple book.
- Hope Spot: During her imprisonment, Akari sees a cat and manages to tie a paper to it, hoping that someone would find her location. However, it's revealed that the cat's owner is Teruhiko's accomplice, and that Teruhiko used the cat precisely to make Akari hope for something and not go mad from despair.
- Lampshade Hanging: Josuke's backstory is full of holes and pretty improbable, especially since his savior couldn't be found afterward. To distract Josuke during their fight, Takuma begins to point these holes out and entertains the possibility that Josuke may have had traveled to the past to save himself, which is a known fan theory. However, Josuke doesn't care that much.
- Locked Room Mystery: When Koichi and Rohan discover Hanae Orisaka's corpse, it seems that she has had a grave car accident in her kitchen, with nothing out of the ordinary inside her locked house besides Hanae. The two quickly deduce that a Stand is responsible, and they aren't as interested in the method of the murder as finding the culprit, on whom they obtain a clue.
- Most Writers Are Writers: Chiho, who is still one of the main characters, is an aspiring novelist in search for material and inspiration for her first book.
- Orphan's Plot Trinket: Takuma possesses a black jewel necklace, which belonged to his mother Akari and was a gift from Teruhiko. It serves as the final clue to make Teruhiko understand that Chiho is having a relationship with her half-brother.
- Photographic Memory: Takuma's Stand ability. It might not seem like much, but he can use it to force his opponents to experience his memories with their mind making any injuries they experience real.
- Rescue Romance: Chiho was saved by an unknown student from a mugger several years before the events of the book and her savior became her idol. Chiho develops a friendship and then a romance with Takuma because she learns that Takuma is her savior. What she doesn't know is that it was a ploy from Takuma himself made to make her fall in love with him.
- The Blade Always Lands Pointy End In: The story averts this trope, as Takuma knows he must carefully gauge the distance between a target and him so that his knives do land on the blade as they rotate in midair.
- Villain Protagonist: Takuma is the protagonist of the story, but also its villain, whom Josuke and co. are trying to catch.
- What Is This Thing You Call "Love"?: Takuma finds himself unable to truly love his half-sister (if not in the romantic sense, at least in a familial sense), at most having some affection for her.
- Your Mind Makes It Real: The Book is able to make people relive one of Takuma's memories, and the body is fooled to the point it will change to reflect the memory. It can be very dangerous if your body begins to think it has been hit by a speeding car.
