Ordinary factory worker Junichi Namase (played by Ryunosuke Kamiki), who aspires to become a painter, falls in love with an unremarkable girl, Megumi Yamamura (played by Fumi Nikaido). On Christmas Eve one year, after finishing overtime, Junichi rushes to a jewelry store, filled with excitement as he chooses a ring to propose to Megumi. Unexpectedly, a jewelry robber, Shunsuke Kyogoku (played by Kota Watanabe), bursts in and changes Junichi's life. To protect a little girl, Junichi is shot in the head. Whether it can be considered fate's blessing, Professor Hiroshi Tamamoto (played by Masato Ibu), a neurosurgeon at the hospital affiliated with Toho University, performs the world's first brain transplantation on Junichi, but for some reason, he conceals the outcome from the public. After miraculously being brought back to life, Junichi brings joy and anxiety to Megumi's heart. However, the revived Junichi seems to undergo subtle changes both physically and mentally; his emotions become increasingly unstable, and he feels out of touch with everything around him, uncontrollably spiraling down a path of unknown violence... This film is adapted from the novel of the same name by Keigo Higashino.