He appears inside the Science Lab while Ayumi looks around and tries to attack her. She manages to run away from him and he fall through the hole. He then appears in the end of the chapter in the middle of exorcism and yells at Ayumi. He and Yuka both tell her the truth about the school and them and leave to bring Satoshi along.
He appears along with Yuka and Satoshi and start torturing Ayumi, but they are all interupted by Sachiko appearing and using the magic of the book to make them dissapear. Ayumi later finds him inside the Incinerator room and apologises to him by giving the heart-shaped chocolate. After Ayumi comes back to apologise to Satoshi, he appears and they all go back to the gravesite where they bury the book. Ayumi kisses Yoshiki saying that she thinks that she loves him and they all say their goodbyes as Ayumi leaves the school. After that Yoshiki's soul can finally rest in peace.
Significant plot details end here.
In Corpse Party D2: Depths of Despair he died by burning alive in the Science Lab.