YOU SAID:
He wrote a letter, only to realize he didn't know her address.
INTO JAPANESE
彼は手紙を書きましたが、彼女の住所を知らないことに気づきました。
BACK INTO ENGLISH
He wrote a letter, only to discover that he did not know her address.
INTO JAPANESE
彼は手紙を書きましたが、彼女の住所を知らないことがわかりました。
BACK INTO ENGLISH
He wrote a letter, but it turned out that he did not know her address.
INTO JAPANESE
彼は手紙を書きましたが、彼女の住所を知らないことが判明しました。
BACK INTO ENGLISH
He wrote a letter, but it turned out that he did not know her address.
Come on, you can do better than that.