I didn't expect this to be so good. It's definitely one of the best stories I've ever read. The plot and execution of dialogues are perfect, especially the comedy and smut—it's so fcking hot, damn. I love both MC Shin and ML William, I swear to god. ML is hella attractive, his expression, personality, and possessiveness towards the MC. While the MC is so precious, he's so pure and funny. I REALLY LOVE THEM. The ending is actually sad. I don't know well, MC waited for ML until he died from old age and will take his soul to the demon realm.
Rengoku no Millennium; A Millennium in Love's Purgatory