Unbeknownst to both sides, the fight that was getting fought inside the Blue Fire Domain had a spectator.
This spectator kept a safe distance from the battlefield and used one of the observation-related Perks to keep tabs on the rankers involved in the fight.
This particular Sansara Perk allowed him to have a bird-eye view of the nearby area. The only limitation to using this Perk was the fact that the user couldn't move from the spot while the Perk was active.
Keeping an ideal position in one place for longer while spying on two teams might not turn out well for most solo rankers. However, this man had no such trouble. That's because he was wearing a beaked mask artifact that hid his presence from everyone's senses, protecting him from potential altercations.
'She did a good job killing those rankers right off the bat. It was such a shame she stopped her insanity after that.'
Eren said to himself and sighed while watching Becky fight.