Check the journal's interior pages and front cover.
Combined pictures investigation
Check the front of the final photo received and the numbers on the back of the photos.
Journal investigation (2)
Check the blue chip on the journal's right page, the text on the journal's left page, and the front cover.
Summary
The Main Character finds a journal in an unusual box in the escape room basement. Its author is Zero, written by hand for fear of losing the memories contained within. Its contents reveal that Zero's master was named Merriweather; the journal serves as a record of their romance. A scenario unfolds parallel to the situation between Luke and the MC, with Merriweather falling fatally ill and trying to remove herself from Zero's life and memories. This causes an argument about the scenario's unfairness, with Luke arguing in favor of Merriweather's actions and the MC arguing against them.
The two realize there's one final clue they haven't used and discover a second journal, revealing Merriweather ultimately had second thoughts about her decision, backed up Zero's memories prior to their deletion, and allowed them to be together in her final years. A note from Sphynx awaits them at the end, and the two rush to check the sign-in logs to find out who last completed the escape room.