YOU SAID:
図書館に本を返すのを忘れないでよ。
INTO JAPANESE
図書館に本を返すのを忘れないでよ。
BACK INTO ENGLISH
Don't forget to return the book to the library.
INTO JAPANESE
その本を図書館に返却することを忘れないでください。
BACK INTO ENGLISH
Don't forget to return the book to the library.
You've done this before, haven't you.