Before the Day

After the execution of alleged killer Shiori Okuma, three university friends are suddenly transported seven years into the past—right before the serial teacher murders began—where they encounter Shiori as a fugitive claiming her innocence, prompting them to uncover the truth behind the case that could change everything.

Kotaro, Hayato, and Rin are transported seven years into the past, where they encounter Shiori—a woman who, in their original timeline, was executed for a series of teacher murders—now a fugitive suspected of the first killing but insisting on her innocence; divided over whether to trust her, the trio attempts to save Shiratori, the known second victim, yet despite their efforts they fail, while Rin, tasked with watching Shiori, unexpectedly grows closer to her, leaving Shiori’s actions at the time of the murder unclear and the suspicion surrounding her only deepening.

Kotaro, Hayato, and Rin, transported seven years into the past, try to prevent the serial teacher murders using knowledge from their own time, but a third killing occurs, with Miyaji—previously seen acting suspiciously—becoming the victim; as their leads disappear and Shiori goes missing just before the murder, suspicion toward her intensifies, leading Rin to believe she is the culprit and urging the others to focus on returning to their own time, even as new evidence places Shiori near the scene of the crime.

As evidence places Shiori near the scene of the third murder, Rin becomes convinced she is the culprit, but Kotaro and Hayato hold off on reporting her and instead investigate the victim Miyaji’s movements, discovering he was at a live music venue around the estimated time of death—suggesting someone else may be responsible; as they draw closer to the truth, Shiori makes a surprising request, asking to learn about the next incident.

After uncovering Shimoyama as the true culprit behind the serial teacher murders and confirming Shiori’s innocence, Kotaro and his friends return to their own time to find that history has changed—Shiori is no longer on death row, and Shimoyama has been sentenced instead; using footage from the past, they begin producing a documentary about Shiori’s near wrongful conviction, but as they reach out to detectives connected to the case, they uncover a new anomaly—something that should not have happened is now unfolding.

After realizing that their actions in the past have altered the present, Kotaro and his friends decide to return to 2019 once more to uncover the truth behind the case that ended with Shimoyama’s arrest and to save Detective Ito, who was never supposed to die. Successfully traveling back in time again, they discover that two weeks have passed, Shiori is no longer wanted, and she has mysteriously disappeared. With the GPS tracker no longer working and no clues to Shiori’s whereabouts, the group turns to Detective Ito, who had been obsessively pursuing her, hoping he may hold the key to the truth.

Kotaro and his friends reveal to Detective Ito that they have traveled from 2026 and join forces with him to search for Shiori. When a new sighting of Shiori is reported, Ito finally catches up to her, but she escapes at the last moment, and Ito is suddenly attacked from behind. At the same time, Hayato learns from one of Rin’s classmates that Rin once had a disturbing fascination with imagining ways to kill people. His suspicions deepen further when footage from a hidden camera at the scene of the upcoming fourth murder appears to show Rin herself in the past, forcing the group to question whether she may be connected to the killings as the next murder case begins to unfold.

After preventing the fourth murder in the Teacher Serial Murder Case and saving both Samejima and Rin’s friend Marimo, Kotaro spots the fleeing culprit and gives chase in his van. However, he is suddenly engulfed in a mysterious light and time-slips alone back to 2026. There, he discovers a horrifying new reality: the villa burned down seven years earlier, and the bodies of an unidentified man and woman were found in the ruins. Fearing for Hayato and Rin, Kotaro desperately searches for a way to return to 2019 once again.

After learning that Hayato and Rin are in mortal danger in 2019, Kotaro discovers how to time-slip once again and returns to the past, rescuing them from a villa engulfed in flames. During the incident, he witnesses Shiori fleeing the scene, further deepening the mystery surrounding her. Meanwhile, Detective Ito regains consciousness after being attacked while investigating Shiori and becomes convinced that she is the culprit behind the serial murders. As a police manhunt begins, Kotaro uncovers a crucial clue hidden within Ito’s investigation notes, bringing him closer than ever to the truth behind the Teacher Serial Murder Case.

Shiori reveals to Kotaro that ten years earlier, Nagine committed a murder to protect her, and that she took the blame for the crime herself. Yet despite insisting on her innocence in the recent killings, Shiori suddenly confesses to being responsible for the entire series of murders. Refusing to believe she is the true culprit, Kotaro vows to clear her name and convince Detective Ito that someone else is behind the crimes. As the investigation reaches its climax, the search for the real murderer intensifies, the fate of the still-unfolding fifth murder hangs in the balance, and the shocking truth behind the Teacher Serial Murder Case is finally revealed.