The studio made quite a few changes to the story in this episode compared to the game version, although the overall goal is still the same. I can't really blame them for compressing the story and focusing on the important parts, since from my perspective, this is only a fraction of the story in the series. That said, it's difficult for me to view the episode through the eyes of an anime-only viewer without my experience with the games influencing my opinion. From that perspective, the biggest issues are the fast pacing and the lack of explanation. On the other hand, this episode does give a chance for the little sisters an opportunity to shine.