Found in her apartment in Tokyo's Shibuya district on Christmas Eve, it has taken the Tokyo Medical Examiner's Office more than six weeks to conclude that Iijima, 36, died of pneumonia.
But few believe that is the full story.
Iijima was an outspoken AIDS activist in a country where stars are generally unwilling to involve themselves in causes that could associate them with an issue or incite a whispering campaign. Commentators have now linked her death to the disease.
"No-one will ever be able to say she had the disease, but she never stated it clearly and that gave her authority," said Toshiko Marks, a professor of multicultural understanding at Shumei University.
Her AIDS campaigning began in 2000, around the time she released the book "Platonic Sex", which sold more than 2 million copies and been turned into a television drama and movie.
In the book she detailed being raped in her teens, having an abortion and running away from home. To survive, she worked as a hostess and drifted into the porn industry, quickly rising to be one of the best-known stars, appearing in more than 100 titles.
Iijima used that exposure - and her refreshing frankness - to move to daytime talk shows.
Iijima kept up a blog, even after her retirement from the media world in 2006. She used it to reveal her health problems and tabloids reported she was suffering from mild neurosis, cystitis and kidney complaints.
But musing on her blog kept coming back to AIDS.
In a post dated December 2nd, 2007, she wrote, "Today, someone is dying from AIDS. Every day, the number of people infected is increasing.
"My first test took a lot of courage and was very frightening until the result came back. I still remember being worried," she wrote. "For the people who are important in your life, you should take the test."
According to the Japan HIV Centre, around 15,000 Japanese have tested positive for the illness - but as many as four times that number are unaware they have the disease.
A memorial service for Iijima is scheduled for March 1, with all donations going to the Japan Foundation for AIDS Prevention.