Takahisa only stirred in his unconscious sleep. Armin would then notice that Takahisa's soul crystal had it's flame slightly get brighter but it was still dim, meaning that at least Takahisa was slightly getting better.
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The door to the office was left unguarded as the other man had left to go downstairs, to where the gunshots continued. Maybe Kaika had started up something by accident, but it would serve as a perfect kind of distraction for Eren go into the office and see the "boss" for himself.