Both are historical fantasy dramas with a similar feel and vibe between the leads that begin with the FL rescuing the ML who is instantly taken with her but she treats him more like a child and calls him an odd endearment ("monster" vs. "little one"). Years later the FL returns with a different, harsher personality, and the two seem to be on opposite sides, but the ML is still in love. Both have an identical scene where the FL is invisible, spying on the ML, but he senses/sees her anyway. Both plots involve a magical and dangerous sword that the ML has.