Almost My Floor (UP)

Chapter 4, after the incident with the firecraker, you will go down the elevator and watch a short cutscence. When you regain control, take out your phone and dial a new number: 678876. This will call the cleaner's phone, leaving you free to pick up her cleaning supplies.

Then, use the cleaning supplies on your apartment door to the far left, completing the slider minigame to unlock this.