In fact, I never managed to finish the main game due to the tedious gameplay, but I could still play this without being spoilered (...I think)!
Unlike the main game, this DLC is purely a Visual Novel. No boring and endless-seemingly map walks chasing some random demon clouds. You just follow the story and at some points you have 2 options to chose from for the later outcome of the story. Total playtime was roughly 3 hours for me.
Aside from the DLC's main story (which happens somewhere in the middle of the main game), there are also some kind of additional mini gags / conversations between some characters of the game.
All in all, if you miss the combat system from the main game (which I kinda doubt), you might be disappointed, but if you are looking for some lovely side-stories, its definetly worth a try.