The act of the Sword Spirits changing their master was an extraordinary event.
Having served William, they naturally held themselves in high regard. Suddenly being told to serve a girl of a mid-level Soulmancer's caliber was indeed hard for them to accept.
If William did not seal their power, a mere release of energy from them could easily incapacitate many mid-level Soulmancers.
However, William was true to his word. If he said that Alice would be the future master of the Sword of Soulbreaker, it meant Alice would possess complete dominion over the two Sword Spirits.
The Sword Spirits would stand no chance if they tried to defy Alice's commands.
If Alice wishes, a single thought can erase the two Sword Spirits that have existed for millions of years.
This was the true reason for the Sword Spirits' despair.
Hearing what the Sword Spirit said, Alice immediately became unhappy: "Soullet, do you not like me?"