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.