In 1910, Yi returned to Korea and started teaching at Oshan Elementary School (; ). He resigned (left his job) in 1915. In 1916, he studied overseas again in Japan, entering Waseda University, but he dropped out in his third year. In 1918, he went into political exile in Sanghai because of his involvement with Korean independence movements and New Korea Youngman Praty (; ). In 1919, he was a functionary of Provisional Gavement of Korea (; ).