The Entity That Settled In At Work

Not long after I joined the company, my mother came to drop off something I'd forgotten and mentioned that there were ghosts standing in the corners of the room and along the walls. (She said there was one floating near the ceiling too.) They weren't malicious, and since I couldn't see them, I didn't mind and focused on my work, eventually forgetting all about it. (It wasn't a haunted property.) One year, the number of staff decreased, and for efficiency... they boldly removed the walls, making it a single open floor. However, the restrooms couldn't be moved due to piping issues and remained standing alone in the center. Come to think of it, what happened to the ghosts...? After closing one day, a senior colleague who was on restroom duty was cleaning the women's restroom when they heard the sound of running water from the adjacent men's restroom. Thinking another employee had cleaned it, they said thank you, but were told no one had gone into the restroom... They rushed to check, but it wasn't just uncleaned; it wasn't even wet... they complained about it later with a pale face. At that time, my mother happened to pass by, and I had her look from the entrance. She said they were densely packed in the restroom and the situation was bad. She couldn't see the area where the restroom was, it was pitch black, and she was too scared to go near it... Later, the senior colleague replaced the light bulbs with brighter ones and put down salt offerings, but it's unclear if it had any effect. However, When I walk past there, I can still hear the sound of running water, even though no water is flowing.