Last year, one of the biggest films in South Korea was a swashbuckling tale of freedom fighters battling against a cruel oppressor: Japan.

In Choi Dong-hoon's "Assassination" ("Ansatsu" in Japanese), which opens here this weekend, a trio of underground operatives led by sharpshooter Ahn Ok-yun (Gianna Jun, also known as Jun Ji-hyun) is tasked with killing a Japanese general and his Korean collaborator in occupied Seoul during the 1930s. An entertaining mash-up of period melodrama and spaghetti Western-style action, the film raked in over $85 million at the South Korean box office, making it the country's second-highest-grossing flick of 2015.

That commercial performance was certainly impressive, but it paled in comparison to the previous year's biggest earner. Historical epic "The Admiral: Roaring Currents," a lavish recreation of Yi Sun-sin's famous victory over the fleet of Toyotomi Hideyoshi in 1597, is the most successful movie of all time in Korea, where it earned in excess of $117 million. (Unlike "Assassination," the movie went straight to DVD in Japan.)