Tools:
Charles 3.4.1

Firefox

Steps:

1. Open Charles
2. Enter Ninja Saga (click to play)
3. Enter your character and check that he is equipped with a Kunai (lvl 1 weapon) If not, purchase from shop.
4. Refresh Ninja Saga. Now, do not select your character
5. Look in charles and find this url 'http://app.ninjasaga.com'
6. Expand until you find the line '(SystemData.get)'
7. Right click this line and select Breakpoints
8. Now, select your character and click play in Ninja Saga
9. The loading should freeze and a Breakpoint tab appears in Charles
10. Click Execute 3 times
11. 
12. Click "Edit Response" and select the "AMF" tab
13. Expand the 'weapons' > Expand 'wpn1'
14. 
15. You should see the line 'damage' with a value of 7
16. Change this 7 to 888 or any value you want. This will be your Kunai Damage.
17. Click back on the Structure tab and right Click the 'SystemData.get' and Click on Breakpoints
18. Click back on the Breakpoint tab and click Execute
19. The game will now load. Fight any mission with your Kunai and watch your high damage.