Just for context I'll attach the preceding sentence as well:
Does この世界に modify あとから入ったもの or is この世界に a local adverb, saying: "In this world,...
I'm having problems with あとから. So far, my textbook only taught me about あと as a suffix, basically meaning "after". However, I've never seen あと attached to to a particle, so I'd rather see it connected to から as a prefix, making "あとから", which would somehow indicate a timespan starting after a certain point in time.
先輩の世話をさせられる. I guess the subject of this causative passive are the 者 who are coerced to help their sempais?^^