YOU SAID:

i want to be his one and only.

INTO JAPANESE

私は彼の唯一のものになりたい。

BACK INTO ENGLISH

I want to be his only one.

INTO JAPANESE

私は彼の唯一の一人になりたい。

BACK INTO ENGLISH

I want to be the only one of him.

INTO JAPANESE

私は彼の唯一の一人になりたい。

BACK INTO ENGLISH

I want to be the only one of him.