Eren’s first big mission as a newly-minted member of the Scout Regiment is…cleaning a dusty old castle that once served as the Regiment’s HQ. It’s not glamorous, but it is a good opportunity for him to meet his new comrades, among them Petra, Oulo, Eld, and other people with funny names.
But despite those funny names, they’re all elite soldiers with dozens of Titan kills and perhaps hundreds of assists between them. Whatever his status is here (and it’s not high), he intends to soak up as much as he can from these veterans of his calling.
After dinner, those veterans clear out when Eren shows curiosity in Hange Zoe’s activities experimenting on Titans. Hange ends up talking to Eren the entire night before she’s to perform some tests on him to get a better idea of what the regiment has to work with. She also proves to be the most knowledgeable person on the Titans either he or we have yet encountered.
Not only that, Hange is a very odd duck in a regiment full of ’em, but there’s a method to her madness. As she tells Eren, she enlisted and was once driven solely by hatred for humanity’s “mortal enemy,” but the closer she got to the Titans, and the more she learned about them, the more the hate faded and the desire to learn still more grew. They may be a voracious plague on mankind, but that doesn’t change the fact that Titans are inscrutable, wondrous creatures.
Part of that wonder is derived from the fact that Titans are so light for their size, which makes Hange consider the possibility that they way humans perceive Titans and the way Titans really are may be two completely different things. The show has been so extremely stingy with solid info on the Titans, so theories of this nature burnish their mystique.
Fear and rage haven’t gotten humans far, so she has always strove to study them from a different perspective, and with that has come an ungrudging admiration of and affection for her “subjects”. I never thought Titans could be portrayed with something like compassion, but Hange’s interaction with them does just that.
So when, the morning after the whole night she talked Eren’s ear off, those subjects, named Sonny and Bean, are discovered having been murdered, she’s genuinely devastated and flips out. Meanwhile, Erwin seems to have a plan that diverges from the “company line”, which Mike has sniffed out. No doubt Eren is integral to that plan, whatever it consists of.
Eren has learned in no time at all that he’s in a strange place full of intrigue among strange people who want to use him for one reason or another. He’s passed the Don’t-Get-Eaten-By-A-Titan Test, but surviving in a swirling sea of eccentric, erratic, and ambitious personalities is a whole new ballgame.