The plot is so linear that I expect the Pandora's Box to be the ???-Rank Relic, and all the relics in the world come from it or something (since the Pandora's Box cause a disaster once opened, and relics always have 'evil tendencies'). Then the Crow following MC around is Huginn from Norse Mythology, and he ate 'the Hope' remaining in Pandora's Box, then used it on MC to save the world from relics.
I guess that would make sense since the plot just revolves in a 10km radius around the MC, and it is so easy to guess things.