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.
