Almost never do you see an isekai genre go in so much depth about a main character's past. At most, it will be quickly glossed over with no real substance. Re:Zero, unlike its counterparts, puts real meaning into understanding the character and the decisions MC has made up to this point, and does it in such a way that strikes you deep down to the point where you feel the same intense emotions as the characters. This episode finally gave conclusion to everything Subaru went through from season 1, and that conversation he had with Rem in episode 18. This episode essentially has Subaru turned completely around and look directly at himself and his mistakes. It explains the kind of mindset Subaru was in throughout Season 1 when coming into this world, especially why he acts the way he did, and helps the audience understand the self-hate that he harbored for himself, the one that is resolved by episode 18 of season 1 when Rem gave Subaru the courage and tenacity to keep moving forward. Having forgotten everything in the past constructed by Echidna in the trial, he needed to find that will again. This was essentially a test to see whether Subaru can confront his past and overcome the burdens that he carried throughout his childhood and most of season 1. And I must say.. the way this was depicted was absolutely beautiful.