This is an expansion~
He chooses to climb stairs to exercise. He had never paid attention to the rumor that "there was a male corpse built into the corridor wall." He also didn't think carefully about why every time he came back from the night shift and stood in front of the corridor, the corridor light would quietly light up all the way to the fourth floor - the floor where he lived. Until one day he accidentally took the elevator and a bloody head hung from the top. "Why are you hiding from me? I turn on the lights for you every day."
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