A local movie that depicts the difficult life of Koreans forced to work as sex slaves for Japanese soldiers during World War II snatched the top spot at the box office on Wednesday, data showed.

"Spirits' Homecoming," shown in 507 theaters and cinemas on its opening day nationwide, attracted 153,783 moviegoers, beating American superhero film "Deadpool," which garnered 138,057 viewers, according to Korean Film Council (KOFIC).

Its surprise performance was not entirely unexpected as it had enjoyed high pre-sale reservation rates in the run-up to the opening.

Based on the testimonies of the so-called "comfort women," who were forced into sexual servitude at Japanese military brothels, the movie took its cinematic motives from "Burning Women," a drawing by Kang Il-chul, one of the victims, during her therapy sessions.

Historians estimate that up to 200,000 women, mostly from Korea, were forced to work in the front-line brothels during the war. Korea was under Japanese colonial rule from 1910-45.

The movie, 14 years in the making due to a lack of financial resources, was finally able to see completion after crowd-funding 12 billion won ($970,000) from South Korean supporters. But finding a distributor and local cinemas that were willing to show it proved to be equally challenging, especially when South Korea struck a deal with Japan late last year, to put the comfort women issue to rest. The opening date, originally scheduled for December, was pushed back.

But online petitions to shed light on the meaningful movie finally encouraged big movie chains like CGV and Lotte Cinema to respond and increase the number of screenings.

In Seoul, a high school teacher voluntarily rented a local cinema to screen the film in memory of those wartime victims.

"Stories about the film having difficulty finding cinemas made me think what I, as a history teacher, could do to help spread its screening," said Choi Tae-sung, a teacher from Daekwang High School in Seoul, who is popular among students for his online classes on Education Broadcasting Station (EBS).

"Regardless of the deal between South Korea and Japan, it is our duty to remember our painful history and its victims," Choi said, referring to the diplomatic deal reached in December between the two countries. (Yonhap)