Sugata Kentaro is a former professional player of a Japanese chess-like board game known as shogi. (The manga's title comes from the 81 squares on a shogi board.) After leaving the pro circuit, Sugata enters the world of "Shinkenshi" ("true sword-masters"), or players who gamble on shogi and other board games like go and mah-jong. He meets his match in Nakashizu Soyo, a female Shinkenshi who happens to be a part-time maid in Akihabara.