TOKYO (AP) -- Masahiro Nakai, one of Japan's top TV hosts and a former pop star, said Thursday he was retiring to take responsibility over sexual assault allegations that are part of a wave roiling Japan's entertainment industry and have triggered an avalanche of lost advertising at one of the networks where he worked.

Weekly magazine Shukan Bunshun reported in December that Nakai had reached a 90 million yen ($580,000) settlement with a woman over the alleged sex assault at a 2023 dinner party that Fuji TV staff allegedly helped to organize. He acknowledged "a trouble" and a settlement, while denying any violence, in a statement earlier this month. The magazine has also alleged that Fuji TV has long exploited its female announcers to entertain stars like Nakai.

"I, Masahiro Nakai, is retiring from entertainment activity as of today," Nakai said in a statement distributed to his paid fan club and posted on social media by apparent members. Japanese media also confirmed and reported his retirement.

"I am truly sorry for causing trouble and losses to so many people," Nakai said, and repeated his "sincere apology" to the woman. "I'm really, really sorry for saying good-bye this way ... Sayonara."

Japan's entertainment industry is in the midst of a wave of sexual assault cases, including the abuses of hundreds of boys and young men by late talent mogul Johnny Kitagawa, whose now-defunct agency Johnny & Associates managed many boy bands, including the one to which Nakai belonged, SMAP.

Last Friday, Fuji TV President Koichi Minato acknowledged the company had been aware of the problem six months before the magazine report and hadn't disclosed it. Minato apologized and said Fuji TV would investigate the case but also said he believed his employees had not done anything wrong.

After dozens of commercials were withdrawn, Fuji TV apologized for causing trouble to advertisers and agencies but declined to disclose details.

Following shareholders' demands for further clarification about the scandal and steps the company had taken and what measures are planned, Fuji was set to have a special board meeting later Thursday.

Nakai said in his statement that he has sorted out all negotiations of terminating his shows and contracts with television, radio and sponsors. He said he has yet to taken all his responsibility and promised to "face various problems and respond sincerely."

Fuji Television Network's vice-chairperson Ryunosuke Endo, who is also head of Japanese commercial broadcasters' association, in a televised live news conference Thursday noted Nakai's retirement was his "personal decision" but said Nakai was part of the upcoming investigation and that he hoped for his sincere cooperation.

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AP video journalist Mayuko Ono contributed to this report.