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.