After graduating Waseda University in 1981, Inada became a lawyer in 1985. She first belonged to the Osaka bar association and has belonged to the Fukui bar association since 2008. She stood for the government in a lawsuit relating to Yasukuni Shrine, and served as an attorney for the plaintiff concerning the "Contest to kill 100 people using a sword" that occurred during the Second Sino-Japanese War, as well as the commanders who fought in the Battle of Okinawa and a bereaved family suing Kenzaburō Ōe and Iwanami Shoten for their defamation of character towards the commanders. When she served as an attorney for the families of the plaintiff concerning the "Contest to kill 100 people using a sword" that occurred during the Second Sino-Japanese War, she tried to win her points relative to the convicted war criminals in court. But her side lost in court, because the judge at Supreme Court of Japan admitted some testimonies. After the failure of the trial, she hoped to become a politician.
The House of Representatives (衆議院, Shūgiin) is the lower house of the National Diet of Japan.
The Diet can be dissolved by the Prime Minister at will, preceding an election. The most recent was by Shinzō Abe on November 21, 2014.
On 15 August 2005, after being "spotted ... when she addressed a ruling-party audience on Japan’s war crimes in 2005", Inada was nominated as an official candidate of the LDP by Shinzō Abe (later the Prime Minister). Inada ran in the general election held on 11 September 2005 and was elected to the House of Representatives for the first time.
The 45th Japanese general election was held on 30 August 2009. Inada was re-elected to the House of Representatives with 50.0% of the vote. Inada's main opponent, DPJ candidate Ryūzō Sasaki, obtained 45.6% of the popular vote.
The 46th Japanese general election was held on 16 December 2012. Inada's primary opponent was JRP candidate Kōji Suzuki. Inada won with 52.6% of the popular vote. Kōji Suzuki got 22.9% of the vote.
The 47th Japanese general election was held on 14 December 2014. Inada was re-elected to the Diet with 64.8% of the vote. Inada's main opponent, JIP candidate Kōji Suzuki, obtained 26.5% of the popular vote.
In the Diet, she served as a member of the judicial committee, and the special committee for the establishment of political morals and the amendment of the Public Officers Election Act. From January 2008 to December 2008, she was also a member of the committee for General Affairs. In 2012 she was appointed as Minister of State for Regulatory Reform in the new Abe Cabinet. She held this post until September 2014.
Inada is highly esteemed by Abe because of her political and historical beliefs, which are close to Abe's. Inada believes in the spirits of Shinto. Abe appointed her Chairperson of the LDP Policy Research Council in September 2014, even though the position is usually reserved for party members with longer political careers.
Despite having no military experience, Inada was named Defense Minister by Prime Minister Abe on August 3, 2016. Inada is the first Defense Minister since Akinori Eto to have no record of prior military service. Inada is also the first female defense minister since Yuriko Koike, and the second female Defense Minister in Japanese History.
On September 15, 2016, one month after becoming Defense Minister, Inada met with American Secretary of Defense Ash Carter in Washington, D.C. After the meeting, Inada stated that the Japanese military would increase its activity in the South China Sea and increase the number of military drills with the United States, which represented a significant change in Japanese policy regarding the South China Sea dispute.
In December 2016, immediately after Abe and Inada met U.S. President Barack Obama in Hawaii and Abe expressed 'everlasting condolences' for the casualties of the 1941 attack on Pearl Harbor in Hawaii, Inada made her first visit to the Yasukuni Shrine since becoming defense minister. Inada's visit followed by a day a visit to the shrine by Minister for reconstruction Masahiro Imamura. Both visits prompted protests from China and South Korea and created calls for Japan to express similarly prominent condolences to its Asian neighbors.
On February 4, 2017, Inada met with the new United States Secretary of Defense James Mattis in Tokyo, Japan. In the meeting, they discussed North Korea, as well as the Territorial disputes in the South China Sea. Mattis also reaffirmed the United States's commitment to the Mutual Defense of Japan.
On Monday, May 1, 2017, Inada ordered the dispatch of the Maritime Self-Defense Force Helicopter Carrier Izumo to protect a U.S Navy supply vessel in the Pacific. This marks the first time the Japanese Navy has been used to defend allied vessels since the 2016 amendment to the Japanese Constitution.
Before the Tokyo assembly election, on June 27, 2017, Inada stated that a particular candidate (of the Liberal Democratic Party) was supported by the Defense Ministry, the Self-Defense Forces, and the defense minister. As the defense force is not supposed to get involved in politics, this statement prompted heavy criticism and forced Abe to apologize, without going as far as following Renho's suggestion to sack her.
Inada resigned in late July 2017 over claims that she helped to cover up internal records that exposed the danger Japanese peacekeepers faced in South Sudan after the Defense Ministry partially released information it had found on a computer.
Following her historical and political beliefs, Inada is affiliated with the openly revisionist lobby Nippon Kaigi. These beliefs are sometimes characterized as "right wing" though Inada reportedly rejects that phrase, and "conservative".
Yasukuni Shrine, a Japanese Shinto shrine to war dead who served the Emperor and Japan during wars from 1867–1951, has been controversial, due to the enshrinement of International Military Tribunal for the Far East war criminals. But, Japanese nationalists have been paying respect at the shrine. In 2006, Inada said, "Any Japanese national, who criticizes Japanese Prime Minister's visit for paying respect at Yasukuni Shrine, could be the person who cares nothing for the souls of dead Japanese soldiers at the war and such a Japanese national could be deprived of the right to comment on anything about Moral/Upbringing." and "Yasukuni Shirine is not the place for the oath of peace, but the place for the oath to fight desperately against the aliens at the risk of Japan, following the honored spirits of the dead soldiers at Yasukuni Shrine."
Inada questioned why the 2007 film Yasukuni (produced by Chinese director and some scenes of the movie were politically expressed by Chinese side) received Japanese government funds, and said that such funds should not be given to films with a "political agenda".
Inada was a supporter of right-wing filmmaker Satoru Mizushima's 2007 revisionist film The Truth about Nanjing, which denied that the Nanking Massacre ever occurred. After Takashi Kawamura, Mayor of Nagoya City, made denialist statements about the Nanking Massacre, on 6 March 2012 in Tokyo, at the Simposium to support Kawamura's statement, she opposed to the history class in the Japanese school education, because the teachers, who could be members of Japan Teachers Union and be sympathized with China, teach the pupils about the Nanking Massacre of the Second Sino-Japanese War at the school classes. At that time, she said, "When Japanese Prime Minister definitely denies the Nanking Massacre, such a non-sense school education could end."
Inada insisted that The International Military Tribunal for the Far East after World War II, was against the principles of the modern law and the International Military Tribunal for the Far East was only a part of the policy of Supreme Commander for the Allied Powers during the Allied occupation (mainly United States' occupation) of Japan after World War II, and she also said that Japan should totally deny the historical viewpoints, which too much emphasized the Japanese military invasion in China, following the decision of The International Military Tribunal for the Far East. In August 2015, Inada expressed her intent to form a committee to verify the authenticity of the tribunal and the views of Japanese history it employed. "Inada has argued that the Tokyo Trials distorted Japan's responsibility for the war", according to the Wall Street Journal in 2016.
Inada was shown smiling in a picture with Kazunari Yamada, leader of the National Socialist Japanese Labor Party (NSJAP), who has praised Adolf Hitler and the 9/11 attack on the World Trade Center. But, after the photo was released by the press, she said publicly that she was unaware of his career. A staff member of Sanae Takaichi, Minister of Internal Affairs, whom she was with at that moment, said that he "was an assistant for an interviewer", and "We had no idea who he was back then, but he requested a snapshot."
Inada was a signatory to the "The Facts" advertorial, supported by The Society for the Dissemination of Historical Fact and published in The Washington Post on 14 June 2007. The advertorial asserts that there is no proof of the Imperial Japanese Army's system of Comfort women during the Pacific War. She also helped to launch the LDP Special Mission Committee to Restore the Honor and Trust of Japan, which in 2015 recommended to Prime Minister Abe that Japan counter what it views as false allegations against Japan regarding the Comfort Women issue. When the committee demanded that an American textbook publisher correct its depictions of comfort women that were "at odds with the position of Japan," Inada called these depictions an "infringement upon the human rights of Japanese children living in the United States." "In 2012, ... Inada wrote in a newspaper column that 'there is no need for an apology or compensation' to women who served Japanese soldiers sexually in World War II because she said the Japanese military and government didn’t compel the women to perform such services," the Wall Street Journal reported at the time of Inada's appointment as Defense Minister. On the other hand, in a 2013 press conference, Inada called the Comfort Women system a grievous violation of women's human rights.
"In one incident in 2011, South Korea barred ... Inada and other Japanese lawmakers with conservative views from entering the country", The Wall Street Journal reported in a review of Inada's career in 2016.
In 2015, when Prime Minister Abe prepared the statement on 70th anniversary of the end of World War II, Inada said, "No need to express the word like remorse", "stop continuing to apologize [to China and other Asian countries]", "military invasion is not appropriate word [to express the Japanese action in Asian countries before the end of the war]".
In 2015, Inada went against her party's traditional opposition to LGBT rights by setting up a committee within the party to discuss the matter.
Several members of the anti-Korean resident hate speech group Zaitokukai made donations to the political funding organization of Tomomi Inada between 2010 and 2012, which seems to show close ties.