Binding vows hold great importance in the Jujutsu Kaisen Universe. All jujutsu sorcerers consider it to be an important tenant of Jujutsu sorcery. Binding Vows are essential contracts that someone can forge with themselves or another person using cursed energy.
Following the rules and constraints outlined in these contracts can lead to increased power or the accomplishment of a goal, while violating a binding pledge has uncanny consequences.
Binding Vows With Oneself
Self-imposed vows can be damaging to the creator. For instance, voluntarily limiting the amount of cursed energy for a period of time, can enhance the quantity of cursed energy and cursed techniques available to the user.
Cursed energy responds to the desires of its unique user as a consequence of negative emotions. As a result, the user can boost the power of their cursed energy by imposing a self-imposed "Cursed Restriction" that makes using their skills more dangerous.
By disclosing one's cursed technique, for example, one increases their risk by causing their cursed energy to swell in reaction to the user's resolve. Showing One's Cards is a Binding Vow that boosts the user's cursed energy in exchange for loudly revealing how their cursed technique works.
Kento Nanami uses a Binding Vow called Overtime to limit the amount of cursed energy he can access while working for Jujutsu High. Nanami's cursed energy increases substantially once his regular shift ends and he begins working overtime.
Binding Vows With Others
These are cursed energy binds contracts made between two or more individuals. Both parties must agree to a specific set of terms that benefit them both. Breaking a Binding Vow with others carries a significantly harsher penalty than breaking a self-imposed Binding Vow. In the anime, the vow shown so far is between Ryomen Sukuna and Itadori Yuji.
Sukuna proposed a Binding Vow after Yuji's body had died, allowing him to heal in exchange for allowing Sukuna to assume control for one minute anytime he stated a keyword.
On the condition that Yuji forgets about the commitment, he also promised not to kill anyone during that time.
In reaction, Yuji initially rejected and demanded a fight to the death. Sukuna imposed stipulations as a compromise. Sukuna will revive Yuji without the Binding Vow if Yuji wins.
If Sukuna succeeds, Yuji will be forced to accept the Binding Vow and lose all memory of it. Yuji was promptly defeated by Sukuna, who forced him to take the pledge.