People in Britain, draw the sword in the stone at the beginning

Roa is a time traveler, and traveled to Britain in the moon world to become a subordinate of the famous witch Morgan.
At this moment, it happened that Merlin spoke about the sword in the stone, claiming that "the one who pulls out this sword will be the Chosen King", but Morgan had already seen through Merlin's tricks, and asked Roa to take advantage of this opportunity to get rid of the sword early. Infiltrate the enemy's interior as a knight, and find the right opportunity to assassinate the new king.
Roa knew the plot. He knew that Morgan had sent many 'assassins'. After these assassins surrendered, they could even become Knights of the Round Table, so Roa passed.
According to his idea, he should fail to assassinate Artoria, and then take advantage of the trend to become a Knight of the Round Table.
but...
Holding the sword in the stone, looking at the scene where the knights directly declared their loyalty to him, even Roa didn't know what to say, just... the new king is me?