YOU SAID:

Why are you doing that?

INTO JAPANESE

お前はなぜそうする？

BACK INTO ENGLISH

You are why to do so?

INTO JAPANESE

あなたはこれを行う理由は?

BACK INTO ENGLISH

You are the reason for doing this?

INTO JAPANESE

あなたがこれを行う理由ですか。

BACK INTO ENGLISH

That's why you do this?

INTO JAPANESE

だからこそこれを行う?

BACK INTO ENGLISH

That's why you do this?