[2026] What was the cause of death of Hirata Runa? Summary of deaths of DIANNA Project trainees

DIANNA Project Nagoya trainee, Runa Hirata, passed away on September 25, 2026, at the age of 8, due to myocarditis caused by influenza. This article summarizes the official announcement, the circumstances leading up to her death, her profile, her last X post, and messages from her family.

[2026] What was the cause of death of Hirata Runa? Summary of deaths of DIANNA Project trainees

Q. What was the cause of death of Hirata Ryuna?

A. The official announcement from the DIANNA Project states that the cause was "myocarditis associated with influenza."

Q. When did he/she pass away?

A. He passed away around 4:00 AM on September 25, 2026, and this was announced on his official website and on his personal X account on September 28, 2026.

Q. How old were you?

A. I was 8 years old. I was active as a Nagoya trainee for the Nagoya-based girls' idol project "DIANNA Project".

table of contents

1. Official announcement regarding the death of Ryuna Hirata
2. The events leading up to his death (chronological order)
3. Hirata Runa's Profile
4. Last X post and message from family
5. What is myocarditis associated with influenza?
6. Fan reactions
7. Frequently Asked Questions (FAQ)

1. Official announcement regarding the death of Ryuna Hirata

On September 28, 2026, the DIANNA Project posted an announcement on its official website regarding Nagoya trainee Hirata Runa, stating that Nagoya trainee Hirata Runa had passed away due to myocarditis resulting from influenza. She was 8 years old.

It has been reported that the wake and funeral were held privately with only close relatives in attendance, in accordance with the wishes of the bereaved family. The official website expressed its deep gratitude to the fans and those involved who have supported the artist, and asked that they refrain from making individual inquiries, interviews, or asking questions on social media, out of consideration for the feelings of the bereaved family.

👉DIANNA Project Official Website

On the same day, his official X account (@DP_HIRATALUNA) also announced, prefacing its statement with "We apologize for this sudden announcement," that he had passed away around 4:00 AM on September 25, 2026.

2. Circumstances leading up to death (chronological order)

The officially revealed events, in chronological order, are as follows:

The timing of the influenza infection and the progression of the illness from the onset of symptoms to death have not been made public.

3. Profile of Hirata Runa

According to the ZAKⅡ article, her official website profile states that she was born on April 16, 2018, and that her hobbies include gaming and traveling. She also has experience appearing in a commercial for "Leisure Pass Tokai."

Her X profile stated, "I'd be happy if you called me Luna-chan." Her posts included the hashtag "#JS2," indicating that she was a second-grade elementary school student attending school while participating in these activities. Her friendly way of speaking, often ending sentences with "gozaru," was also a characteristic of her posts.

The DIANNA Project, to which she belonged, is a Nagoya-based girls' idol project with a total of seven groups. Hirata performed on stage at regular shows as a trainee.

4. The last X post and a message from family

Last post before death

🔗 Hirata Runa Official X

Hirata's last post before his death was on September 20, 2026, along with a photo he took in the city after a regular performance. He wrote, "Thank you again today," expressing his gratitude for the performance, and also sent his best wishes to the performers in the third act who were to appear afterward.

Message from family

On September 28, 2026, a message written by her was posted on her official X account along with a video of her from before her death. It read, "One-third of Ryuna's life was spent as an idol," and conveyed to her fans her wish to keep her in the hearts of her fans as an eternal idol. The message concluded with Hirata's characteristic "Thank you very much."

In another post, she expresses her gratitude to her fellow idols who have been kind to her, her fans who have supported her, the staff at the agency who made her an idol, and everyone who has been involved in her career.

5. What is myocarditis associated with influenza?

Myocarditis is a disease in which inflammation occurs in the heart muscle (myocardium). The heart's pumping function is impaired, making it unable to adequately send blood to the rest of the body, which can lead to arrhythmias, heart failure, and in severe cases, sudden death.

According to the Department of Cardiology at the National Center for Child Health and Development, influenza virus is listed as a cause of myocarditis in children, along with enteroviruses and RSV. They explain that in "fulminant myocarditis," which develops rapidly, the heart's pumping function may be impaired, and life-threatening arrhythmias may occur.

Please note that Ms. Hirata's specific symptoms and treatment progress have not been made public.

6. Fan reactions

According to a ZAKⅡ article, following the news of the death, expressions of grief spread on X, with many posts using words like "8 years old," "suddenly," and "unbelievable." There were also many messages of condolence, acknowledging that influenza should not be taken lightly.

7. Frequently Asked Questions (FAQ)

Q1. What kind of activities was Hirata Ryuna involved in?

A. As a Nagoya-based trainee of the girls' idol project "DIANNA Project," I performed on stage at regular shows and other events. I also have experience appearing in a commercial for "Leisure Pass Tokai."

Q2. Will there be a funeral or memorial service?

A. It has been announced that the wake and funeral were held privately with only close relatives in attendance, in accordance with the wishes of the bereaved family. There has been no announcement regarding a memorial service.

Q3. When was your last performance?

A. Her last post on X before her death was a comment she made after performing at the "DIANNA Project Regular Performance vol. 70" on September 20, 2026.

Q4. Do you have any requests for fans from your agency?

A. Out of consideration for the feelings of the bereaved family, we are asking on our official website that you refrain from making individual inquiries, conducting interviews, or asking questions on social media.

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