YOU SAID:
They're there for their own reason
INTO JAPANESE
彼らは自分の理由でそこにいる
BACK INTO ENGLISH
They're there for their own reasons.
INTO JAPANESE
彼らは自分の理由でそこにいます。
BACK INTO ENGLISH
They are there for their own reasons.
INTO JAPANESE
彼らは自分の理由でそこにいます。
BACK INTO ENGLISH
They are there for their own reasons.
That didn't even make that much sense in English.