It consisted of 25 letters, 12 letters to send and another 12 to receive for the respective months of the year and an additional letter for August 13, designed to help students learn many words and model sentences.
1年12ヶ月の往信返信各12通と8月13日の1通を加えた25通からなり、多くの単語と文例が学べるよう工夫されている。