In 1905, the Eulsa Treaty was made between Japan and Korea, making Korea a protectorate of Japan.
Kim participated in a mass protest against the treaty in Seoul and presented a memorial to Emperor Gwangmu urging him to withdraw from the treaty.
In 1908, Kim joined New People's Association, a national-level underground organization established by Ahn Changho for nonviolent Korean independence movement.

In 1910, the Japanese colonial government arrested An Myung-geun (안명근; 安明根) for plotting to assassinate Governor-General Terauchi Masatake.
Kim, who was a close friend of An, was suspected of being an accomplice and arrested as well.
Like other jailed suspects, Kim was severely tortured, but no evidence linking him to the assassination attempt was found and he was released from prison after 3 years.

This term of imprisonment left Kim with damage to cartilage and his left ear disfigured for life, due to beating by Japanese in the prison, in addition to his calves that were already permanently scarred in his earlier imprisonment torture for the killing of Tsuchida.
At the time, Han Pil-ho (한필호; 韓弼昊), a member of Sinminhoe, was killed, Shin Suk-choong (신석충; 申錫忠) killed himself, and An tried to commit suicide during the severe interrogation but failed.
Kim also tried to kill himself with a self-inflicted injury in his head, but failed.

In prison, Kim changed his name from "Kim Changsoo" to "Kim Koo" and adopted the pen name of "Baekbeom" (백범, 白凡).
Kim stated in his biography that the change of his name symbolized breaking free from Japanese nationality records and that he chose the pen name Baekbeom, which means "ordinary person", hoping every ordinary Korean person would fight for the independence of Korea.
In 1905, the Eulsa Treaty was made between Japan and Korea, making Korea a protectorate of Japan. Kim participated in a mass protest against the treaty in Seoul and presented a memorial to Emperor Gwangmu urging him to withdraw from the treaty. In 1908, Kim joined New People's Association, a national-level underground organization established by Ahn Changho for nonviolent Korean independence movement.
In 1910, the Japanese colonial government arrested An Myung-geun (안명근; 安明根) for plotting to assassinate Governor-General Terauchi Masatake. Kim, who was a close friend of An, was suspected of being an accomplice and arrested as well. Like other jailed suspects, Kim was severely tortured, but no evidence linking him to the assassination attempt was found and he was released from prison after 3 years.
This term of imprisonment left Kim with damage to cartilage and his left ear disfigured for life, due to beating by Japanese in the prison, in addition to his calves that were already permanently scarred in his earlier imprisonment torture for the killing of Tsuchida. At the time, Han Pil-ho (한필호; 韓弼昊), a member of Sinminhoe, was killed, Shin Suk-choong (신석충; 申錫忠) killed himself, and An tried to commit suicide during the severe interrogation but failed. Kim also tried to kill himself with a self-inflicted injury in his head, but failed.
In prison, Kim changed his name from "Kim Changsoo" to "Kim Koo" and adopted the pen name of "Baekbeom" (백범, 白凡). Kim stated in his biography that the change of his name symbolized breaking free from Japanese nationality records and that he chose the pen name Baekbeom, which means "ordinary person", hoping every ordinary Korean person would fight for the independence of Korea.
Kim Gu