Eren could already feel that the restrictions around the entire Academy had been strengthened. Even if he wanted to think that it was a coincidence, he knew that this was far from a coincidence.
Now that Mist was back and expected him to be in the Academy, it was only a matter of time before he found his identity. As he was in a hurry to save his disciple, he didn't have time to slowly assimilate in the Academy after all.
"Can you do it faster?" he asked the Ghost Queen.
"Do you think I am making some noodles here? This is a delicate process. A little mistake and the seal might become ineffective," the Ghost Queen said, slightly irritated at constantly being poked to hurry.
She knew that Eren didn't know how hard her work actually was. All he was doing was commanding her and expecting things to process faster.