I have no doubt that after the fight is done the demon will lose a bunch of power and get the manga cover form of a loli, will be a sad day.
The novel is very different, I checked it out on ncode where it was originally published, is not uncommon for WN to get changes from editors when they get adapted into light novels, for exampleintroducing a female character earlier to add fanservice, a beach episode or some stupid event because the editor have nothing to do with a good work and they have to come with bullshit to explain their paycheck.
For example in Shield Hero the chocobo race early in the story (manga) was not present in any way in the novel, and MC would have likely refused to play the bitch game that early in the story.
In the original WN MC decides to summon her only after hearing some rumors about demon cards selling "low" because they can rebel and curse their owners to death, so when it would still give him hundred of millions he just summons her, she arrives as a bratty loli that treats him like garbage.