An independent candidate opposed to the central government's plan to deploy a U.S.-developed missile defense system in Akita defeated the ruling party incumbent in the northeastern constituency in Sunday's upper house election.

Shizuka Terata, 40, was jointly fielded by major opposition forces in Akita, where the Defense Ministry's conducted a faulty geographical survey for the deployment of the land-based Aegis Ashore missile defense system.

(Shizuka Terata)

She beat Matsuji Nakaizumi, 40, a first-term lawmaker of Prime Minister Shinzo Abe's Liberal Democratic Party.

The neck-and-neck race drew attention as it was viewed as a de facto referendum on the proposed deployment of the missile system in a Ground Self-Defense Force training area in the prefectural capital's Araya district on the Sea of Japan.

Reflecting the government's desire to press ahead with the deployment plan, Abe and his right-hand man, Chief Cabinet Secretary Yoshihide Suga, delivered stump speeches in Akita.

Both Tokyo and Washington were closely monitoring the outcome of the race. A U.S. Embassy source in Tokyo has said the ruling party candidate's loss could hamper the system's deployment in Japan.

The Defense Ministry has sought to deploy the system, aimed at countering the threat of North Korean missiles, in Akita and the western Japan prefecture of Yamaguchi.

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(Photo taken on Jan. 18, 2019, shows the Aegis Ashore land-based missile defense test complex on Kauai Island, Hawaii.)

But the plan to host the Aegis Ashore system came under fire in the run-up to the House of Councillors election after the ministry's geographical survey used to select Akita as a candidate site was found to have contained numerical errors.

The Aegis Ashore deployment is unpopular among residents, concerned about damage to health from radar and electromagnetic waves emitted by facilities that could become a target in an armed conflict.

During campaigning, Terata, who is the wife of opposition-affiliated independent lawmaker Manabu Terata, pledged to block the deployment while refraining from highlighting her party affiliation in the hope of gaining support from unaffiliated voters.

The LDP's Nakaizumi criticized the Defense Ministry but did not clarify whether he supports the deployment of the defense system.

The LDP had secured a seat in the Akita constituency in the past three upper house elections.