I don't think that will be the ending per say, I feel some external being is going to try to correct this situation and that Machino will want this because of guilt. Her harem will disagree, abiding her guilt and creating a solution that keeps them together, whether the game goes or Machino does.My prediction is....the ending will be like they will go back to the game and mc comes back to a normal life
I think the others will get as much exploration, but Olivia has been consistently the character with the most wrinkles. She's been the odd-man-out for the whole time she's been around, and has needed the most convincing to work with the rest of the cast (for understandable reasons). She reminds both Machino and the audience that Machino's situation is incredibly abnormal, and due to her strong understanding of how the real world works, she's the one with the strongest grasp of how messed up the situation is on some conceptual level.I think people are jumping ship to Olivia way too quickly. Don't forget that others so far mostly had a glimpse of their backstories because we were getting an abridged version from Machino's perspective. Olivia just happens to be the first one that was examined in detail. For all we know, future heroines could have a backstory just as good or if not even better than her.