DIAMOND IS UNBREAKABLE
In 1999 in the town of Morioh located in S-City, M-Prefecture, Josuke Higashikata (東方 仗助 Higashikata Jōsuke, the kanji 助 suke, can also be read as jo) is one of the more popular guys in high school and becomes quick friends with one of his classmates, Koichi Hirose. But when Josuke's nephew Jotaro Kujo (who happens to be quite a bit older than he is) shows up, things get truly crazy. One of DIO's henchmen has brought the Bow and Arrow to Morioh and someone has been using it on various people in the town creating Stand users—as discovered when one of them, the murderer Anjuro "Angelo" Katagiri, uses the power of his Stand Aqua Necklace to get revenge on Josuke's grandfather for putting him in prison. When Josuke and Koichi go to investigate Koichi is struck by the arrow, unleashing his Stand Echoes. They discover that the culprits are Okuyasu and Keicho Nijimura, whose father - formerly DIO's lackey and injected with DIO's cells - has now turned into a monstrous creature with DIO's death. It is then revealed Keicho wants to create Stand users in the hopes that someone will be able to kill his monstrous father. Josuke manages to show the brothers that their father is still at least partially human inside and dissuades them from their activities. However they are attacked by the Stand Red Hot Chili Pepper, which kills Keicho and takes the Bow and Arrow. Okuyasu joins with Josuke, Jotaro, and Koichi to fight the Stand that killed his brother and eventually becomes close friends with Josuke. The group then continues to encounter other Stand users while looking for Red Hot Chili Pepper's user.
Koichi soon takes center stage when he is kidnapped by his psychotic classmate Yukako Yamagishi, also a Stand user, who is in love with him and is determined that he will love her back. He escapes from her and in the process his Stand evolves into a stronger form. The group then finally comes face-to-face with Akira Otoishi, Red Hot Chili Pepper's user. However, he proves hard for the group to defeat. Only when Joseph Joestar, the father Josuke never knew, arrives in Morioh are they finally able to defeat Akira. The Bow and Arrow are then taken into the Speedwagon Foundation's custody and all seems to be over for the moment.
A month later Koichi meets manga author Rohan Kishibe, whose Heaven's Door ability allows him to open up a person's face like a book and both read and rewrite their memories; Rohan finds himself drawn to the plucky Koichi, but does not get along with Josuke. Yukako and Rohan both become part of Josuke's group of Stand users along with others the group has encountered, such as Tamami Kobayashi, Toshikazu Hazemada, Mikitaka Hazekura, and Yuuya Fungami.
Soon afterwards, Koichi and Rohan discover a hidden alleyway in town that is not of their world. Once they enter, it is there they meet the ghost of a young girl named Reimi Sugimoto, Rohan's babysitter in his youth, who was murdered by a serial killer over a decade before. She begs Koichi and Rohan to find her killer, who has stayed in Morioh and is still preying on innocent people. This turns out to be Yoshikage Kira, a serial killer that kills women using his newly acquired Stand Killer Queen to explode their bodies and keeps their hands as romantic mementos. When Josuke and Okuyasu's new friend, Shigekiyo "Shigechi" Yangu, discovers Kira's secret and is killed for it, they resolve to put an end to Kira's murders.
Jotaro and Koichi eventually fight Kira, but before he can be fully defeated, he flees and forces Aya Tsuji, the user of the Stand Cinderella, a Stand that can alter people's physical features, to change his face and kills her before she can tell Josuke what he now looks like. Shortly thereafter, the ghost of Kira's father uses a second Stand-creating Bow and Arrow to create an army of Stand users to protect his hiding son and go after members of Josuke's group. Rohan eventually suspects Kosaku Kawajiri is Kira's new identity and confirms it after reading Kawajiri's son Hayato's memories. However Rohan is killed instantly by Killer Queen's new technique, "Killer Queen Bite the Dust", which Kira acquired after accidentally being stabbed with the Bow and Arrow. The ability plants miniaturized Killer Queen on a person which kills anyone that tries to learn about Kira from them, as well as protects that person. When they learn Kira's identity, Killer Queen enters their field of vision, then enters their eye and explodes. The period of time in which the victim learns his identity and the bomb explodes is repeated in-loop until Kira learns who the bomb killed.
When Rohan's death is repeated a second time, Josuke, Koichi, Okuyasu, and Jotaro were there to meet him. They see Hayato and figure out Kira is masquerading as his father, all dying as a result. The memory is then repeated again so Kira can learn who was killed, but this time Hayato tricks him into giving his own identity away before Rohan's death. He then has to remove the technique from Hayato to protect himself as he fights Josuke, resulting in an end to the time-loop. With help from Josuke, Hayato, Okuyasu, and Koichi, Jotaro delivers a blow to Yoshikaga Kira that propels him in front of a fire truck and he is run over. Kira is then shown as a ghost as his first victim, Reimi, informs him what happened. Kira attempts to attack Reimi once more, only to be torn apart by countless phantom hands, presumably of his other victims.
With Kira dead and their murder solved, Reimi and Arnold say their last goodbyes to Josuke, Rohan and the other Stand users of Morioh as the two spirits ascend to heaven. As Jotaro and Joseph prepare to leave Morioh, Josuke wishes them the best, but not before using Crazy Diamond to snatch Joseph's wallet.