"Kara no Kyōkai 8: Shūshō" serves as an epilogue to the "Kara no Kyōkai" film series, tying together narrative threads and providing closure to the overarching story. The film is divided into two segments: "Future Gospel" and "Future Gospel -extra chorus-." The first segment, "Future Gospel," centers on Mikiya Kokutou and Shiki Ryougi, who are now in a stable relationship. Mikiya works as a private investigator, while Shiki continues her enigmatic existence, occasionally assisting him with cases involving the supernatural. Their lives intersect with Mana Ryougi, a young girl who claims to be Shiki's daughter from the future. Mana possesses a unique ability to foresee death, which she uses to prevent tragedies. Her presence forces Shiki and Mikiya to confront their past and the lingering consequences of their actions.

The second segment, "Future Gospel -extra chorus-," shifts focus to a side story involving Tomoe Enjou, a character from earlier in the series. Tomoe, now living a quiet life, encounters a mysterious woman named Mitsuru Kamekura, who is connected to the series' broader themes of fate and causality. Their interactions explore the idea of moving forward despite the weight of past traumas, echoing the central themes of the series. Both segments emphasize the interplay between time, memory, and identity, reinforcing the philosophical underpinnings of the "Kara no Kyōkai" universe. The film concludes with a sense of resolution, offering a poignant reflection on the characters' journeys and their acceptance of the inevitable passage of time.