It could be said that Eren had underestimated Levine.
She administered a radical potion to both of them after their sixth consecutive session. This potion was enough to mess with his senses.
The Master-ranked potioner told him it was derived from some ranked ingredients that were hard to get in the local herbs market. The potion's effects were very potent even for someone like Eren.
He started seeing the world in weird colors and the objects around him seemed to have lost their shapes. He started hearing smells, tasting sounds, and seeing things that were not really there.
Eren's soul sense was also not spared by the potion. His mental connections with Reen, Alephee, Argo, and those who he had branded were all affected by the potion's effects as well.
