Ex. - character a has a Sp of 50 and character b has an Sp of 25. 50 : 25 = 2 : 1. So for every chance the person with a Sp of 50 has a 2 to 1 chance of hitting their opponent. Paper use 12 pieces. Assing numbers to the characters. 5-12 for character a and 1-4 for character b. Every 2 pieces of paper character a has b has 1.
If character a is attacking and 5-12 come up then the attack hits. If 1-4 comes up then the attack misses. If character b is attacking and 1-4 comes up then the attack hits. If 5-12 comes up then the attack misses. If you have a dice and want to do it like that then make 3,4,5,6 character a and 1,2 character b.
Be carful for certain techniques like kaioken, bukojutso, and punch. They play with the odds. You have to double the speed, or give better chances to another character. You have to refigure it all out.
Character a uses kaioken doubles his Sp. 100:25. Now the odds are 4:1 for him hitting or missing. So another set of papers is needed. Now use 10 pieces. 3-10 character a hits and misses if it is 1-2. 1-2 character b hits and 3-10 he misses.
Punches double a persons chances of hitting. Character b would have 2:2 chance of hitting. That is 50%. If you use a dice 1-3 would be hit and 4-6 would be miss.