Sunset Shimmer never fell through the mirror- instead, she left Equestria altogether. After getting trapped in an underground library of the Moon, losing all perception of time, becoming a nihilist and teaching herself dark magic, she ends up being rescued by Twilight Sparkle- Equestria's newest princess. The rest, as they say... is a mistake of epic proportions history!

The sex tag is mainly just because of a few suggestive lines. Profanity, on the other hand, is something I use all the time... so discretion is definitely advised.