YOU SAID:

Koreans were grateful for how advanced south Korea became thanks to japan. he forgot he was in north Korea.

INTO JAPANESE

韓国人は日本のおかげで韓国になった高度な南に感謝していた。彼は北朝鮮にいた忘れていた。

BACK INTO ENGLISH

South Koreans was grateful thanks to Japan made Korea Advanced South. He was in North Korea was forgotten.