In Korea, he is remembered as a martyr due to his participation in the 1932 Sakuradamon incident, in which he attempted to assassinate the Japanese Emperor Hirohito with a grenade.

However, while there, he was arrested and detained for eleven days because he had a letter from a friend in his pocket that had Korean writing on it.

But one day he witnessed a Korean customer being scolded for being unable to speak Japanese fluently.

[d] On December 6, 1930, he boarded a ship in Chikko, Osaka, and departed for Shanghai, one of the hubs for independence activists in exile.

He eventually learned from a ticket inspector the location of the Shanghai Korean Residents Association [ko] (SKRA), which happened to be secretly harboring the KPG at that time.

After the drinking started, he raised his voice and asked the table: "If it's so easy to kill the Japanese emperor, why haven't Korean independence activists done it yet?

[k] Even if I were to live another thirty-one years, how enjoyable would old age be compared to the free-spirited life I had previously?

Through the connections of Kim, Lee found an ironworking job, and eventually achieved a degree of economic stability.

Meanwhile, Kim worked on acquiring weapons for the attack, but progress was slow due to the financial difficulties and political issues that plagued the KPG.

Lee became intoxicated a number of times and loudly sang songs in Japanese, which drew the ire of onlookers.

He stayed for ten days at the Japanese tailor's house again, and pressed Kim for the grenades so he could go to Japan.

[1] On December 13, Kim Ku and Lee went to the house of An Gong-geun (the younger brother of another famous activist An Jung-geun).

[1][2] Lee then swore this oath:[1][l] In order to restore independence and liberty to the fatherland, I do solemnly swear to become a member of the Korea Patriotic Organization and to slaughter (도륙) the leader of our enemy country.They took a photograph to commemorate the occasion.

On either December 28 or 29, Lee saw an article in the Tokyo Asahi Shinbun that said that the Emperor would be present at a public military parade on January 8 in Yoyogi Park.

[1] On January 6, after planning the attack, he wrote a quick memoir of his life, but suddenly felt that there was no point to it, and threw it in the trash bin of a restaurant he ate at.

[1] After Korea achieved independence, Kim Gu interred Lee's remains at Hyochang Park, along with those of Yun Bong-gil and Baek Jeong-gi.

Kim later wrote of Lee departing from Shanghai:[1][n] The gentleman's disposition flowed like a gentle spring breeze, but his spirit roared like a raging fire.

When he left Shanghai, there were more than a few women who clung to his collar and shed tears, and among the friends who came to the wharf to wish him well was a Japanese police officer.To Tokyo, Lee carried with him a glowing letter of reference from the chief of police at the Japanese consulate in Shanghai.

According to historian Son Sae-il [ko], there were rumors that after Lee's attack, the chief was demoted and recalled to Japan, where he eventually committed suicide.

On December 20, 1931, Lee allegedly sent a telegram to Kim Ku, asking for 100 yen, as he had spent his travel expenses on alcohol.

Running out of money, Lee pawned the watch Kim bought for him and went to an employment agency to find a quick job.

Ashamed, Lee wrote Kim a letter that read "I spent money like a madman, and I've since racked up debts even for my meals.