This items is used to replace the broken belt on the Cassette player in the Language Lab and play back the Cassette Tape (Backmasked Tape).
The hint about this item is in the document named "Property Repair Request Slip".
- The sound recorded on the tape is voices shouting, "Fire!", along with some coughing.
- This will trigger a cutscene in which the Music teacher will talk to Lee Hui-min, revealing the past and dark history of the school and how the seals were made to protect the school from the negative power.
- After that long explanation scene, you are given the Blue Keycard by the Music teacher before he disappears.