Diamond Is Unbreakable

In 1999, in the town of Morioh[lower-alpha 2] located in S-City, M-Prefecture,[lower-alpha 3] a freshman named Koichi Hirose meets a man looking for Josuke Higashikata,[lower-alpha 4] a popular boy in high school. Josuke, who is the illegitimate child of Joseph Joestar, soon encounters the man, who introduces himself as Jotaro Kujo. Jotaro's arrival in Morioh pulls Josuke into the world of the supernatural powers known as Stands, as he becomes involved in Jotaro's search for the Stand-creating Bow and Arrow; Josuke himself is revealed to possess the Stand Crazy Diamond, which has the ability to return any object or living creature (except himself) to a previous state. Josuke and Koichi eventually come across a pair of Stand-using brothers, Okuyasu and Keicho Nijimura. Keicho is revealed to be the one possessing the Bow to create Stand users, turning Koichi into one. After he and his brother are defeated, Keicho is killed by the Stand Red Hot Chili Pepper, which takes the Bow and Arrow. Okuyasu joins with Josuke's group to avenge his brother, encountering several other Stand users before they eventually find and defeat Akira Otoishi, Red Hot Chili Pepper's user, as Joseph arrives in Morioh. The Bow and Arrow are taken into Jotaro's custody and all seems to be over for the moment.

Soon afterward, after Josuke spends time with Joseph, the group encounters other Stand users such as eccentric manga artist Rohan Kishibe, middle schooler Shigekiyo "Shigechi" Yangu and an aesthetician named Aya Tsuji. Koichi and Kishibe later stumble across the mysterious Ghost Street where they meet the ghosts of Reimi Sugimoto and her dog Arnold, learning that they were murdered a decade ago by a serial killer who is still lurking in Morioh. The culprit is eventually revealed to be a handsome office worker named Yoshikage Kira, who seeks to satisfy his murderous urges while living a peaceful, quiet life. Kira has acquired a Stand named Killer Queen, possessing the ability to turn anything it touches into a bomb. When his act of murdering Shigechi to conceal himself backfires (resulting in a brief battle with Jotaro and Koichi in which he is injured), Kira uses Aya to assume the identity of a man named Kosaku Kawajiri, kills them both, and disappears. Kira's father Yoshihiro uses a second Bow and Arrow to create an army of Stand users to protect his son, including a dying cat that reincarnated as a Stand-plant hybrid named Stray Cat, which shoots bubbles of compressed air at its target.

Kosaku Kawajiri's son Hayato begins to suspect that his father has been replaced by an impostor and confronts Kira, who responds by impulsively murdering Hayato. In a panic that he will be discovered, Kira is pierced by Yoshihiro's Arrow a second time, giving Kira's Stand a new ability which revives Hayato. The following morning, Hayato is approached by Rohan, who is investigating whether Kira has assumed Kosaku Kawajiri's identity. After using his Stand to read Hayato's memories, Rohan is blown up by a miniature version of Killer Queen, which had been implanted into Hayato; Hayato suddenly finds himself back in bed on the same morning, one hour earlier. Kira explains that he has infused Hayato with his new ability Bites the Dust, which kills anyone who asks Hayato for Kira's identity and rewinds time by one hour afterward, with the victim's fate cemented regardless of Hayato's attempts to prevent it. The next loop ends with Okuyasu, and Koichi all exploding as well; Hayato wakes up once again, and must get Kira to turn off Bites the Dust within one hour in order to prevent the others' deaths from becoming permanent. Hayato takes advantage of his knowledge of the time loop to wake Josuke up early and arrange for him to overhear Kira blowing his cover, forcing Kira to cancel Bites the Dust just in time to save the group.

Josuke, with help from Hayato and Okuyasu, engages Kira and Stray Cat in a pitched battle; Yoshihiro is blown up after Josuke tricks Kira into targeting him. As Jotaro, Koichi, and Rohan arrive on the scene, Kira attempts to use a paramedic to activate Bites the Dust and rewind time once more, but is stopped by Koichi and Jotaro. Kira is accidentally run over by an arriving ambulance and dies, with Reimi subsequently forcing her killer's soul into being dragged into the underworld. Her mission accomplished, Reimi gives the group her final farewells and moves on to the afterlife. The next day, Jotaro and Joseph return home as the summer of 1999 draws to a close for the residents of Morioh Town.

• Josuke Higashikata[lower-alpha 4] is the main protagonist and illegitimate son of Joseph Joestar. He is a freshman who lives in the town of Morioh with his mother and grandfather. He uses the Stand Crazy Diamond,[lower-alpha 5] which can not only punch rapidly, but also restore objects to their original state or rearrange their structure, allowing him to heal injuries, erase written documents, or revert complex structures to their raw components. He becomes especially enraged if anyone ever makes fun of his pompadour hairstyle.
• Koichi Hirose[lower-alpha 6] is Josuke's and Okuyasu's best friend and is also a freshman in high school, but appears as a short boy. His Stand is Echoes,[lower-alpha 7] which has three distinct "ACTs". ACT 1 and ACT 2 can replicate sound effects and attach them to anything, which result in that happening to the object (e.g. attaching the word "whoosh" causes a gust of wind to blow by) while ACT 3 loses the former abilities and gains the ability "3-Freeze" which causes a target to become very heavy.
• Okuyasu Nijimura[lower-alpha 8] is one of the two Nijimura brothers who became friends with Koichi after defeating a Stand user who murdered his brother. His Stand The Hand,[lower-alpha 9] swipes with its right hand which erases whatever it swipes and it can be used to erase space, drawing objects closer to Okuyasu.
• Jotaro Kujo[lower-alpha 10] is the protagonist of the previous story arc, Stardust Crusaders, who travels to Morioh to find his grandfather's illegitimate son, Josuke Higashikata, who is technically Jotaro's uncle despite Jotaro being older than him, as well as investigate the crimes of a Stand user. His Stand Star Platinum: The World[lower-alpha 11]has the ability to stop flow of time advanced since acquiring it.
• Joseph Joestar[lower-alpha 12] is Josuke's father and Jotaro's grandfather who was previously the protagonist of Battle Tendency and one of the main characters of Stardust Crusaders, now an old man and nearly senile. He uses the Stand Hermit Purple which manifests in the form of multipurpose thorny purple vines that allow him to divine information through electrical equipment or be utilized as ropes.
• Rohan Kishibe[lower-alpha 13] is a famous manga artist who recently moved into a house in Morioh. His Stand Heaven's Door,[lower-alpha 14] allows him to temporarily turn a person into a book, with all of their memories written down akin to a novel. Rohan can read the memories, learn their weaknesses and secrets, as well as write down commands that they must follow (usually, "Can not attack Rohan Kishibe.") The power only activates when the target sees Rohan's drawn artwork, but can also activate if Rohan draws something in the air with his finger. Rohan also stars in his own spin-off one-shot series by Araki called Thus Spoke Kishibe Rohan.
• Keicho Nijimura [lower-alpha 15] is Okuyasu's elder brother who caused the outbreak of Stand users in Morioh to create one whose Stand can end the suffering of their father after he was mutated by Dio Brando into a monstrous, addled immortal. Keicho was later killed by Akira Otoishi when saving his brother from an attack by the guitarist's stand. Keicho's Stand Bad Company [lower-alpha 16] is an army of toy soldiers.
• Anjuro Katagiri,[lower-alpha 17] also known as "Angelo" [lower-alpha 18] is a depraved serial killer with an IQ of 160. While on death row for murdering a rich person while staging a post-mortem ransom, Angelo is made a Stand User by Keicho and uses his water-based Stand Aqua Necklace [lower-alpha 19] to escape and resume his killing spree in Morioh before ultimately confronting Josuke, murdering the youth's grandfather before being fused by Crazy Diamond's powers into a stone that becomes Morioh's tourist attraction Angelo Rock.[lower-alpha 20]
• Akira Otoishi[lower-alpha 21] is the main antagonist for the first half of the storyline, an aspiring rock star guitarist who acquired his Stand Red Hot Chili Pepper [lower-alpha 22] through Keicho's actions.
• Yoshikage Kira[lower-alpha 23] is the main antagonist for the second half of the storyline and a mild-mannered serial killer who has been murdering women for over 15 years. His Stand, Killer Queen,[lower-alpha 24] has the ability to completely disintegrate his victims by explosion, leaving no evidence behind.
• Yoshihiro Kira[lower-alpha 25] is the ghost of Kira's father whose Stand Atom Heart Father[lower-alpha 26] allows him to remain among the living to protect Kira from a photograph. Having acquired a Bow and Arrow from Enya prior to moving to Morioh, Yoshihiro uses the arrow to create Stand users in an attempt to keep Josuke's group away from Kira.
• Mikitaka Hazekura[lower-alpha 27] is a strange individual who claims that he is an alien. He befriends Josuke and Okuyasu, and occasionally helps them out. Mikitaka uses the ability Earth Wind and Fire[lower-alpha 28], allowing him to shapeshift into inanimate objects. It's ambiguous whether or not Mikitaka is actually an alien, or a normal human with a Stand.
• Stray Cat[lower-alpha 29], a cat-like plant Stand that is a reincarnation of a cat named Tama [lower-alpha 30] which was accidentally killed after being hit by the Arrow.
• Reimi Sugimoto[lower-alpha 31] is Yoshikage Kira's first victim. She was killed 15 years before the happenings of the manga and waited as a ghost for someone whom she could warn about her killer.
• Hayato Kawajiri[lower-alpha 32] is a shy and intelligent schoolboy who realized his father Kosaku Kawajiri was murdered by Kira when the killer assumed his identity. Though Kira decided to use the boy as a means to kill Josuke's group, Hayato ended up being the killer's downfall.

With Part 4 of JoJo's Bizarre Adventure, Araki said that he moved away from "muscle men" as they fell out of popularity with his readers and he wanted to focus more on fashion. When designing his characters' outfits, Araki considers both everyday fashion and "cartoonish, bizarre clothing that would be impractical in real life." He also forgoes using specific color schemes for his characters and gives his readers different impressions through various color combinations.[5] Araki said that while he drew several character in Parts 1 through 3 naked to evoke Greek or Roman gods, he stopped doing it so much with Part 4 to be a "bit closer to home."[6] Diamond Is Unbreakable is set in the fictional town of Morioh located in S-City, M-Prefecture, which is modeled after the author's hometown of Sendai, Miyagi Prefecture.[7]

In 2000, it was announced that Otsuichi would be writing a novel based on Part 4. The novel proved difficult to complete; in Kono Mystery ga Sugoi 2004, Otsuichi claimed to have written over 2000 pages, but thrown them all out.[50] Intent on writing a novel that lived up to the manga, it took him until 2007 before The Book: JoJo's Bizarre Adventure 4th Another Day was finally released on November 26.[51] It is set after the events in the manga, and includes illustrations by Araki.

In 1997, Araki published the Weekly Shōnen Jump one-shot Thus Spoke Rohan Kishibe ~Episode 16.. Confessional~, starring Rohan after the events of Part 4. In 1999 he wrote the three-chapter story Dead Man's Questions[lower-alpha 34] in Allman magazine. Dead Man's Questions stars Yoshikage Kira, the main antagonist of Part 4. Both Thus Spoke Rohan Kishibe and Dead Man's Questions were later compiled in Araki's one-shot collection, Under Jailbreak, Under Execution, in 1999. The former launched a series starring Rohan, Thus Spoke Kishibe Rohan.

The December 11, 2007 issue of Jump Square featured a second entry into the Thus Spoke Rohan Kishibe collection, entitled Thus Spoke Rohan Kishibe ~Mutsukabezaka~, set seven years after the events of Part IV.

In 2009, Araki wrote the full-color story Rohan au Louvre.[lower-alpha 35] The short story was displayed at the Musée du Louvre as part of their 2009 Le Louvre invite la bande dessinée exhibit.[52] The story was later republished in Ultra Jump in 2010. In 2012, Rohan au Louvre was released in English by NBM Publishing under the translated title Rohan at the Louvre.

In 2011, Araki collaborated with the renowned Italian fashion brand Gucci for the short story Rohan Kishibe Goes to Gucci[lower-alpha 36] in the women's fashion magazine Spur.[53]

In 2012, Araki wrote a third Thus Spoke Rohan Kishibe one-shot for Weekly Shōnen Jump. Entitled Thus Spoke Rohan Kishibe ~Episode 5: Millionaire Village~ it was released in the October 6, 2012 issue of the magazine.[54]

In October 2015, Warner Bros. announced that Part 4 would receive an anime television adaptation that serves as a continuation of David Production's series adaptation.[55] The series aired in 2016.[3]

Toho and Warner Bros. partnered to produce a live-action film based on the fourth arc of JoJo's Bizarre Adventure that was released on August 4, 2017. Takashi Miike directed the film that stars Kento Yamazaki as Josuke. Both studios planned for worldwide distribution and, with a title of JoJo's Bizarre Adventure: Diamond Is Unbreakable Chapter I, are hoping to create sequels.[56][57]