The "red magic sheet" (赤シート, aka shīto) is a popular study tool in Japan. It's a transparent red plastic sheet used in conjunction with study materials that are designed to work with it. Some textbooks are made to use this sheet and sold with this sheet. Important words, phrases or sentences are written in orange letters, and once you cover them with the red sheet, the orange parts disappear!! Surprisingly, if you write something with your ordinary orange pen, the red sheet can make it invisible