Вроде как из новеллы про Ло
[All the new information about Kikoku / Oni Wail ✨]
1. The legend of the sword says that it can destroy entire countries even against the user's will. If anyone too weak were to wield it, they could die on the spot, or have their minds taken over and begin to attack everyone on sight
2. Before Law, only a single swordsman from the Wano Country 200 years ago was able to tame it (because of the strong curse)
3. Kikoku's curse manifests in the "Oni Wail", in which it absorbs the life force in its wielder whenever they try to strike it
4. The only way to master Kikoku is by using Haki, to either overpower the sword's will or to gain the sword's cooperation
-> Since Law couldn't yet use Haki, he tried to tame it through strong emotions. But after he unsheathe it, it rejected him
-> On the second attempt, he finally succeeded in taming it because he understood Kikoku's will and didn't treat it like some wild animal
Kikoku finally accepted Law