YOU SAID:
why was he holding her hand when he's supposed to be mine?
INTO JAPANESE
彼が私のものになるはずなのに、なぜ彼は彼女の手を握っていたのですか?
BACK INTO ENGLISH
Why was he holding her hand when he should be mine?
INTO JAPANESE
彼が私のものであるべきなのに、なぜ彼は彼女の手を握っていたのですか?
BACK INTO ENGLISH
Why was he holding her hand when he should be mine?
That didn't even make that much sense in English.