"Undoubtedly, Yang Yi's authority had been challenged because Annastasia had made decisions on his behalf.
However, the issue needed to be seen relatively. Indeed, Annastasia had made decisions without Yang Yi's consent by allowing Schultz to do what he wanted, but if the Organization of Water couldn't make any decisions without Yang Yi, that would be absolutely unacceptable.
In times of danger, or rather, in crises that required swift decisions, if they could only proceed after Yang Yi's decision, then the Organization of Water would be doomed.
Therefore, when Yang Yi was absent, it was permissible and necessary for someone else to exercise command authority in his place, which was the whole point of having a second-in-command.
However, the issue was that when Yang Yi was absent, it should have been Brian who took charge. So, this 'someone else' should have been Brian. When did it become Annastasia's turn to speak?