Koji Kiyohara (清原 幸治, Kiyohara Kōji) is a tertiary antagonist featured in the spin-off manga Crazy Diamond's Demonic Heartbreak and the light novel Crazy Heartbreakers. He is a university student who shoots Josuke and random civilians of Morioh with a crossbow.
Kiyohara has dark, neck-length hair that is slicked back. He has a wavy strand of hair dangling over his forehead on each side. His irises are small and he has a wide nose. Kiyohara wears a puffer vest on top of a hoodie, baggy pants, and boots. He also wears a watch on his left arm and carries a backpack along with a quiver for his crossbow.
Kiyohara is a sociopathic narcissist who takes pleasure in hunting strangers as if they were animals. He also records videos of him shooting animals to death. Kiyohara believes that he's special compared to others around him and thinks he is the only one with the right to kill people. His ego is hurt when a random teenager like Josuke interferes with his plans.
Kiyohara starts indiscriminately firing bolt at civilians who are running away from an illusionary military helicopter produced from Pet Sounds's Stand. After he happens to shoot a kid in the neck who was running past Josuke, he also fires an bolt at Josuke's back. Enraged, Josuke dashes toward Kiyohara to stop him. Kiyohara shoots another bolt at Josuke, but Josuke easily deflects it with his Stand, surprising Kiyohara. As he wonders who Josuke is, he continues shooting more civilians in the back. He fires at Josuke again and nearly pierces his forehead, but Josuke's Stand grabs the bolt in time before it can go further.
Hol Horse fires two bullets with his Stand, blowing off Kiyohara's ear and a fragment of his crossbow. Pet Sounds starts flying away, momentarily distracting Hol Horse and Josuke, allowing Kiyohara to run away. Hiding in bushes nearby at a park, he waits for Josuke to follow his blood trail while he aims his crossbow. However, Josuke had used his Stand to restore the fragment of the crossbow that broke off and used it to track Kiyohara. Kiyohara is stunned as he hears Josuke's voice behind him, along with his crossbow suddenly being restored. Before Kiyohara could react, Josuke pummels him with punches using his Stand. Josuke steals Kiyohara's money from his wallet and examines his ID. He then ties Kiyohara to a nearby tree using the string from his crossbow. Josuke's grandfather arrives soon after, so Josuke tells him to arrest Kiyohara. Acting like a police officer, Josuke charges Kiyohara with "assault with a deadly bolt".
Kiyohara is taken into custody and the police investigate his home, where they find videos of him shooting animals to death. They intend to do a psychological evaluation on him, which means it might take a long time before he has to go to trial. While sitting in his jail cell, mumbling to himself in fear, a police officer shines a flashlight at his cell. Kiyohara suddenly sees a memory of Kazuki Karaiya sitting beside him in a police car. Karaiya asks him how it felt to lose. When Kiyohara doesn't answer the question but instead asks who Karaiya is, Karaiya screams at him. Pet Sounds then appears behind Karaiya and activates its Stand ability on Kiyohara, causing him to shriek in his cell.