Japanese people born before World War II learned Japanese kana (Japanese syllabograms) writing in a style that is not currently used. These individuals had to learn the current style of kana orthography after the war. An 85-year-old man was taken to our hospital by his family who were surprised by his diary. It was written with kanji (Japanese ideograms) and katakana using the prewar style. A neuropsychological examination revealed impaired recall of hiragana. Neuroimaging studies revealed atrophy of the left fronto-parietal lobe and hypoperfusion of the left frontal lobe. His allographic agraphia might have resulted from the disturbance of the current style of kana orthography.