YOU SAID:
Tom is sitting behind me
INTO JAPANESE
トムは私の後ろに座っています。
BACK INTO ENGLISH
Tom is sitting in the back of my.
INTO JAPANESE
トムの後ろに座っている私。
BACK INTO ENGLISH
I sit behind Tom.
INTO JAPANESE
トムの後ろに座ってください。
BACK INTO ENGLISH
Sit behind Tom.
INTO JAPANESE
トムの後ろに座る。
BACK INTO ENGLISH
You sit behind Tom.
INTO JAPANESE
あなたはトムの後ろに座っています。
BACK INTO ENGLISH
You sit behind Tom.
That didn't even make that much sense in English.