How does the demon Lord know her???? And how did the demon Lord fell in love with her????

From her past life as Tokyo girl

spoiler..........




















After looking at the raws a while back *I do not know Japanese and who knows about my memory with fine details* but it seemed to imply that the demon lord was once a hero, but after seeing her prev life tokyo girl get killed (caused by the king) he grew enraged at the palace and his magic transformed him into the demon lord and destroyed everything and now he evil boi