what if you loved a woman so much you were ready to be exiled for crimes you didn't commit so you wouldn't have to watch her cry, and you were ready to drink poison under threat if it was to protect her, what if you vowed to only let go of her only at the moment the whole world would collapse... but when you reunite with her she talks about loving a different person and how she wants you to live so that her lover can live and then promptly gets shot by an arrow meant for you as you both fall off the cliff.
that's 300 years of yearning and heartbreak etched in the soul. no wonder when the memories made their way to Segye they held so much gut-wrenching sorrow and bitterness that it snowed in summerโ it's the bitter severance of Seori and Yi Hyeon's tie, which i believe was a transgression to the system and hence, led to the ill-fate. also since their souls are from different timelines, it's probably a union that occured before time.
no wonder Cha Segye is a selfish, jealous, expressive, insane person. that's the unsatisfied soul reclaiming all that fate made him let go in his past life.
