That same year, his mother died, and as a result, he went under the care of Duke Gujo Michijanae (구조 미치자네, 九条道実).

When Japan was defeated in World War II, Korea once again became independent and lost its nobility title, as Kazoku was abolished.

Having suffered an unhappy marriage, Deokhye's grief was compounded by the loss of their only daughter who disappeared in 1956, who reportedly committed suicide due to the stress of her parents' divorce.

After the divorce, Takeyuki moved to Kashiwa, Chiba Prefecture, and remarried in 1955 to a Japanese woman named Katsumura Yoshie and had three children, the eldest being Tatsuhito, who succeeded him as titular head of the So family and Count of Tsushima titles.

In 1944, he became a part-time director of the Cabinet Information Bureau and engaged in English–Japanese translation in the Second Section of the War Materials Room of the President's Secretariat.

In July 1945, he was summoned as a second-class soldier and joined the Army's Independent 37th Battalion, transferred to the 83rd Kashiwa Unit.