In the winter of 1895, Kim Koo left for the Qing Dynasty, but upon hearing of the rise of the Righteous Army Corps following the Eulmi Incident, where Empress Myongseong was assassinated, he set off on a journey to return to his homeland. In March 1896, he found a Japanese lieutenant, Tsuchida josuke, disguised as a subject of Joseon(a merchant, according to Japanese records), in a tavern at Chihpo Port.

He took that opportunity to kill Tsuchida based on the patriotic belief that he was avenging the assassinated empress and restoring the country’s honor. On the wall of the tavern, he wrote a declaration in his own hand, “I have executed this Japanese man to avenge our Empress”, and signed it with his own name and whereabouts, “Kim Chang-su of Teotgol, Beagunbang, Haeju”.

Three months later, he was arrested.