Story highlights Tomomi Inada was the country's second female defense minister

She resigned following accusations of a cover-up

(CNN) Japan's Defense Minister has resigned following allegations she helped to suppress the release of sensitive defense documents, the latest blow to Prime Minister Shinzo Abe's Cabinet as his popularity continues to dive.

In a news conference in Tokyo, Tomomi Inada said she submitted her resignation letter to Prime Minister Shinzo Abe on Friday morning, who accepted it. She stepped down the same day the Defense Department released its findings from an investigation into the alleged cover-up, which Inada denies she was a part of.

"I am strongly aware of my responsibility as defense minister to supervise Ministry of Defense and Self Defence Force. I would like to return my one-month salary and decided to resign from defense minister," she said at a news conference Friday morning.

Inada, once a rising political star, assumed the role of defense minister in August 2016 and was seen by many as Abe's successor-in-waiting.

Japan's Defense Minister Tomomi Inada pauses during a news conference on her resignation.

Japan has never had a female prime minister, and Inada is only the second woman to serve as defense minister. The first, Yuriko Koike, was elected as the governor of Tokyo last year. She is also the first woman to hold that position.

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