According to THIS KOREAN ARTICLE, on November 5th, Korean police requested an arrest warrant for a 38-year-old Korean man named Jang, who had been detained the night before, for planning to set fire to the Japanese Embassy in Seoul to protest Japanese "distortion of history and the Dokdo dispute." The man was also accused of planning to take embassy employees hostage.
However, before Mr. Jang was able to carry out his plans, he was arrested by police, who had learned of his plans and traced his whereabouts through his cell phone.
In a statement to police, Mr. Jang reportedly said, "It is vexing and regrettable that I was caught before I was able to carry out the criminal act, but I will keep trying and will not give up until the Japanese attitude changes."
It seems that Mr. Jang had planned to set fire to the embassy, take a hostage, and then hold a press conference to protest Japanese history books and Japanese claims on Dokdo.
According to THIS ENGLISH ARTICLE, when Mr. Jang was apprehended, he was carrying a knife, a lighter, and a copy of a handwritten press statement. The article also says investigators are checking to see if Mr. Jang has any history of psychiatric illness.