the game seems really massive in term of content, all monster supposed to have their own backstory and lore, same with companion, didn't sound like the companion backstory is throwaway either.
post game dlc have a lot of potential here, you can add more monster, or more companion, more magic etc. and the nature of the story being fragmented into book chapter make it they can easily expand the story without messing continuity etc
edit: also, companions being character from stories and legends seems like it can attract those fate/stay night fans. lol