A short-bladed close-quarters weapon, usually double-edged, better suited to stabbing than slashing and easy to carry and conceal.
Sumo's top referees, tate-gyōji, wear a short dagger in their sash, symbolizing readiness to die over a bad call. No one commits seppuku today, but after an overturned ruling the referee still offers to resign; the sumo association customarily refuses.