Recently, preprint papers on LK-99 have been "flooding" the arXiv website because the material was claimed to be capable of room-temperature superconductivity by a South Korean research team. But that may be coming to an end soon: a new preprint paper published on arXiv not only says that LK-99's ability to superconduct at room temperature is an illusion, but also finds the reason for the illusion - cuprous sulfide impurities.