Myocarditis — inflammation of the heart muscle — linked to an influenza infection killed Hirata Runa, an eight-year-old Japanese performer known on stage as Luna-chan, in the early hours of Friday morning, Sept. 25, 2026, according to her agency.
Her family, writing through her official account, confirmed that she died at around 4 a.m. on Sept. 25.
The DIANNA Project, a Nagoya-based talent program and girl-group scheme, counted Hirata among its trainees; the operation develops and markets young J-pop “idols” based on their personality and public image.
A Final Message to Fans
She last appeared on stage five days earlier, at the DIANNA Project’s Regular Live Vol.70 concert in Nagoya, Japan, on Sept. 20. The announcement of her death stunned supporters, who had seen her perform in apparent good health less than a week before.
After the Sept. 20 show, Hirata posted a cheerful note of thanks to the people who came to watch her. “Thank you again today. It was so much fun,” she wrote. She added that she hoped the audience at the show’s third part would enjoy themselves too.
Her bereaved family had wished for a wake and funeral attended by close relatives alone, and the agency said those services were carried out that way.
Her agency offered its deepest gratitude to the fans who supported her and to everyone involved in her short career. Beyond that announcement, no further medical details or treatment history have been released.
Family Asks for Privacy
The family’s tribute, shared through her official account, said they were sorry to deliver such sudden news. Their thanks went out to the fellow idols who had stayed close to her, to the fans who had followed her and to the agency staff who turned her into an idol, along with everyone else who had a connection to her.
“One third of Runa’s life was spent as an idol,” her family said. They said she had loved everyone very much. Supporters, they asked, should hold on to a place for her in their hearts, and they relayed her gratitude for everything up to now.
The agency, noting that the funeral had already taken place in private, urged the public to honor the family’s feelings. It asked that no one direct individual inquiries or media requests to them about her death, and that questions about it not be posted on social media.
In the days after the announcement, a physician told J-Cast that influenza-related myocarditis can progress so quickly that prevention, including vaccination, is the only reliable protection. The outlet reported the comments on Sept. 29.
