South Korea's main opposition Democratic Party and representatives of civic groups rallied on Thursday, protesting Japanese Prime Minister Fumio Kishida's upcoming visit to Seoul.

Kishida is scheduled to visit South Korea for two days from Sunday to confirm cooperation with South Korean President Yoon Suk-yeol. The visit is hoped to pave the way for the Group of Seven summit in Japan later this month. Kishida has invited Yoon to attend the gathering.

Thursday's rally was filled with banners, criticizing Japan for distorting history, exploiting forced Korean labor and comfort women during World War II, planning to release nuclear-polluted water into the sea and forging military alliances with the U.S. and Japan. 

Days ahead of Kishida's trip to Seoul, a verbal duel over disputed islets had been sparked between the two countries. 

On Tuesday, a South Korean lawmaker visited the Dokdo islets (also called the Takeshima Islands in Japan), which are currently under the control of South Korea, but Japan claims them, saying South Korea is illegally occupying them. The Japanese Foreign Ministry said the visit took place despite Japan's opposition and demands for it to be called off, and Japan had lodged a protest against the lawmaker's landing on the islets, which "is absolutely unacceptable."

South Korean Foreign Ministry rejected Japan's protest, calling it an "unfair claim" and said "Dokdo is South Korea's sovereign territory historically, geographically and under international law."

Tokyo and Seoul have long been at odds over issues related to Japan's colonial rule of the Korean Peninsula between 1910 and 1945. The relationship had plunged to the lowest point over wartime labor compensation under the previous administration. 

Relationship has improved under the conservative government of Yoon, who took office in May 2022, with Seoul proposing a solution to the issue in early March.

Yoon paid his first visit to Tokyo on March 16. The two sides agreed to restart reciprocal visits by Japanese and South Korean leaders, which had been suspended since 2011.

However, South Korea's opposition parties have been increasingly critical of Yoon's administration of making compromises to Japan.