When you head back to the Underground for a second time, things are a little different. Sans is a lot more open and caring toward others, which you don't like. Why should he love others when he's all yours to begin with?
For a long time YOU have been wishing for a season three... And hoped you could escape reality for awhile and felt what it would be like to be on a particular show... But what if YOU were given a chance..? Considered as an alien (explanation is in the first chap), You now find yourself inside the show that you fangirl...