SEOUL, South Korea — When the K-pop star Sulli ended her own life last month, her fellow K-pop singer Goo Hara was heartbroken, bidding a farewell to her best friend in a live-streaming video. With tears running down her cheeks, Ms. Goo expressed hope that Sulli would live “as she pleases” in heaven.

“I will live twice more diligently now that you are gone,” she said. “Dear fans, I will be fine. Don’t worry about me.”

But on Sunday, six weeks after Sulli’s death, Ms. Goo herself was found dead in her Seoul home in what the police were calling a suicide. The suicides by two of K-pop’s most beloved stars have left fans in South Korea soul-searching over what has gone wrong in K-pop, their country’s most successful cultural export.

Lee Yong-pyo, the chief of the Seoul Metropolitan Police Agency, told reporters that Ms. Goo’s body was found by a maid on Sunday evening. Investigators also found a handwritten memo in which Ms. Goo expressed her despair, Mr. Lee said.