dai shogi; large shogi variant
A historical large-board shogi variant played on a 15×15 board. Not commonly played today; mainly encountered in historical or game-study contexts.
Dai shogi is a kind of shogi played on a fifteen-by-fifteen board.
He studies old shogi rules and is knowledgeable about dai shogi as well.
From 大 (dai, 'large') + 将棋 (shōgi, 'shogi'). The name reflects the larger board size compared to standard shogi.