cleaver
A single-handed butcher's knife with a square blade resembling a small nata.
Cleavers come in two sizes, small and full size. Small cleavers are generally for home use, they are 180-210mm (7-8inch) in length. Full size cleavers are for professional/restaurant use, they are 220-250mm (9-10 inch).
If the blade is bigger and/or it's double-handed it's a nata. A common weapon for a yandere.