Based on the novel ADONIS. One of the best plotlines ever. Arhad and Ianna having a go at 3rd life together (in a way) but unaware in many ways. GodxDemon in previous life. Awesome swordswoman hated by society because of her mother's deeds, and handsome mysterious guy who's actually illegitimate son of enemy nation which practices inter-marriage and is mysteriously strong. School life but at the same time underworld plot. Story revolving around not only main couple but side characters too. Spirits, elves, dwarfs, beastmen. The novel is just awesome.
https://www.novelupdates.com/series/adonis/
Reminiscence Adonis