Sori joined BTS pack around three years ago, however she doesn't really seems to fit in with her pack mates. Maybe it's just an impression of hers, maybe it's because she's not a born-werewolf, or maybe it's because she doesn't look as pretty as the other girls of the pack...she just feels like she doesn't fit in with them. Add to that the fact that she had been in love with the maknae of the pack for a very long time.