All three are kataba: flat on one face, angled on the other. The angled band is the shinogi.video 2-1
A single bevel drifts left when you push straight down; controlling that drift is the whole skill.video 2-1
Laid "flat", the edge of a single bevel lifts off the board on one side — flesh stays on the bone until you learn the true flat angle. A double bevel (ryōba) sits flat and cuts straight.video 2-1
Thumb firmly on the heel, never floating.video 2-1
Index finger on the spine (mine). Usuba only: index may instead pinch the blade with the thumb.video 2-1
This is the strongest hold — no wobble. Do not drift into a personal style.video 2-1
Whetstones
Lower grit = coarser. #220 brown stone: coarse (arato), for flattening and reshaping chips. Medium stone (nakato): the daily one.video 2-2
One working face only; never flip the stone.video 2-2
Soak until bubbles stop before every use; never dry.video 2-2
Rub the two stones together before and after sharpening to keep them flat; chamfer the corners — they cut.video 2-3
Stack the coarse stone under the medium to raise the working height.video 2-3
Sharpening straight edge, usuba
Shinogi flat on the stone, knife at 30–45° to the stone. Normal grip.video 2-3
Left index and middle fingertips on the shinogi, light pressure — pinpoint, fingertips only; a flat pad on the stone gets sharpened too.video 2-3·video 2-4
Long strokes, forward and back, never short. Only the steel under the left fingers is being sharpened.video 2-3
30 strokes per position; work top of the edge to bottom in about five positions, until the left thumb meets the right. Add water when it runs dry.video 2-3
Flip. Flat face (ura) on the stone, three left fingertips plus the right index on the maker's mark. Burr removal (bari-tori): top, middle, bottom of the edge, then pull through rotating clockwise. Three times.video 2-3
Test: the edge should bite and stop crisply on the corner of the board; if it slides, sharpen again.video 2-3
Used knife: one set. Brand-new knife: three or four sets.video 2-4
Longer knife, more positions along the stone.video 2-5
Curved edges deba, yanagiba
The curved third (sori) sharpened straight up and down becomes straight. For that section move from the left corner of the stone to the right corner, wrist loose.video 2-4
Start at the tip; yanagiba curve is ~10 cm, three finger-widths at a time; past the curve, straight full strokes as usual.video 2-5
Yanagiba burr removal: four fingertips spread along the back, light and even; three passes, blade never leaves the stone.video 2-5
Finishing
Polish the flat faces with a dab of polishing compound on a wet wine cork, on a board you don't mind dirtying. Don't touch the edge. Removes metallic smell and rust.video 2-3
Rinse, wipe dry with paper towel pinched around the blade, never a hand over the edge. Into its case.video 2-3
Flatten the stone in the sink, half then flip and rotate; flat when the two stones suck together and the #220 pattern is even across the face. Wrap in a wrung cloth, stack, store.video 2-5