In Letter Chess, each piece can be considered at the center of a 5x5 square. The piece can move from the central square to any of the indicated black squares. These were the letters that looked the best, to my eyes. Shiatzu is a form of massage, by the way. The game is played by two players on a board of 7 by 7 squares.
Rules are as in usual chess , except that pieces move as indicated by their diagram.
E.g., the letter T piece can move either one or two squares vertically or make a knight jump in the narrow forwards directions or jump two squares diagonally forwards. These kind of diagrams already appear in the book Meta Chess by John William Brown.