Noriaki Kakyouin is a student who ventured to Egypt. Dio Brando, sensing his Stand abilities, requested a demonstration which escalated into a confrontation. Following this, Kakyouin was brainwashed by Dio using cellular buds from his own body, compelling him to follow Dio's command to eliminate Joutarou Kuujou.
The method of Kakyouin's assault on Joutarou varies between the Manga and OVA versions. In the Manga (and the videogame), the attack occurs within a school clinic. In the OVA, he uses his Stand to possess a female student's body for the attack. Regardless, Kakyouin is defeated by Joutarou.
Upon realizing that Kakyouin acted under Dio's influence, Joutarou utilized his Stand, Star Platinum, to extract Dio's implant buds from Kakyouin's head despite the danger of being attacked, thus freeing Kakyouin from Dio's control. Subsequently, Kakyouin joined Joutarou's quest to save Holy and defeat Dio in Egypt.
Kakyouin's Stand, Hierophant Green, excels at long-range attacks and can unleash an energy blast known as Emerald Splash. He exhibits a calm demeanor and is typically seen wearing his green school uniform while often smiling with a composed air, yet humbles himself frequently and occasionally cracks crude jokes to lighten the mood.
From a young age, Kakyouin distanced himself from others due to his inability to trust those who couldn't perceive his Stand. It's suggested that Dio was the first Stand user he encountered, influencing his hesitation and leading to his brainwashing.
Throughout their journey, Kakyouin forms bonds with his companions, serving as a neutral assistant. His critical thinking and strategic planning play a key role during Polnareff's battle against J. Geil. He independently defeats two Stand users, Tower of Gray and Death 13 (the latter whose existence no one remembers), and aids in overcoming D'Arby the Player and Dio Brando.
In Cairo, Kakyouin is killed by Dio during their fight. Just before dying, he unleashes his final Emerald Splash to destroy a clock tower, signaling to Joseph that The World has the power to stop time.
