Possible Clues:

• Japanese writing system
• Japanese writing using Chinese characters
• Pictogram system in Japanese writing
• Characters first seen in Kyushu and neighbouring Japanese islands
• Chinese character in Japanese
• Among these characters, is it possible our seventh letter is read out?
• Letters From Iwo Jima
• Japanese ideograms
• Symbols in written Japanese
• Japanese writing three consecutive letters in return enclosing article