Any normal ranker would be able to sense the deviation in mana signature because the transformation had caused the mana signature to spread around in the vicinity. Meaning an anthrope of Agatha's level cannot conceal their signature once they enter their transformed state.
That or Agatha just wasn't skilled enough yet to do it.
Eren got closer to Agatha while she was in her transformed state. He started looking at her transformed body keenly which put her in an awkward state. But she stood still to let her master continue what he was doing.
Eren started touching her skin and poking his fingers at her muscles. He was also using his mana sense to scan her entire body. Agatha started blushing because the butcher had already crossed the personal boundaries with this very act of his. That too with a straight face on.
'Reen, what do you think?'
Eren asked his beast companion. All his senses were shared with her so she was observing the Anthrope girl with him.
