Although not confirmed, he credits its invention to the late Oyama Yasuharu, one of the most famous professional shogi players in history.
Two players play on a board ruled into a grid of 5 ranks (rows) by 4 files (columns).
From largest to smallest (or most to least powerful) they are: The king is blank on the opposite side, the silver has a lance on the opposite side, the gold a rook, the bishop a tokin, and the pawn a knight.
Promotion values are entirely different from standard shogi: Likewise, when a lance, tokin, rook, or knight makes a capture, it flips back to its former state.
Any trapped piece may be captured and returned to play as part of the opposing army.