Katana is hardened unevenly: the edge is made hard to stay sharp, the spine is kept softer to bend instead of breaking. As a result, the blade combines sharpness and durability rather than becoming brittle

21 2

8 0

30 1

3 0

43 2

21 3

46 1

25 3

29 2

5 0

8 0

28 2

13 2

5 0

22 1

9 0