Ratio Technique forcibly creates a weak point on his target. This is represented by a line with ten strokes, dividing the subject into tenths with the weak point ratio being seven to three.
If the user is able to strike the 7:3 point within the ten strokes, it is delivered as a critical hit. 
Ratio Technique can be used on desired appendages rather than an entire body, allowing the user to target the head, torso, upper arms, and forearms separately or simultaneously.
For a Sorcerer with excellent aim like Nanami, Ratio Technique provides a quick way to end a fight by crippling an opponent's weak points. This allows the user to cleave weaker enemies in two with even a blunt sword and allows them to deal damage to stronger adversaries.
Against adversaries like Mahito, who can heal his body instantly, Ratio Technique is rendered nearly ineffective. Despite hitting Mahito's weakness multiple times, Nanami was unable to deal significant lasting damage to his opponent.
Kento Nanami uses his Ratio Technique to great effectiveness. He's able to deal with low to mid-level Cursed Spirits instantly thanks to the weaknesses exploited by the Ratio Technique. Even against Mahito, who rendered the Ratio Technique next to useless, Nanami was able to utilize this power to momentarily cripple Mahito.
- Jujutsu Kaisen Manga: Chapter 20 (p. 1).