
I guess I can do a very brief summary? Ken and Agia are respective reincarnations of Cain, God of the Moon, and Agio, God of Death. In Amman (the city they reside in), it is believed that humans used to be immortals thanks to Cain (who can resurect people) but Cain was killed by Vercike, the very first vampire according to History, and Agia put a curse on humans: they would become mortals and be prey to vampires until they manage to kill Vercike; every few hundred years, a "human of the moon" and "human of the night" (not sure about the names here but I think that's what they're called) are born, kind of reincarnations of the two gods, and if they both die in the inner sanctum of Amman in some ritual that they call the prophecy it will kill Vercike.
The reality is that vampires existed way before Vercike and used to be slaves to the immortal humans, and though Agio may believe that Cain was killed by Vercike, it seems like it was not the case (Vercike is very much in love with Cain but we don't know exactly what happened at the time). Every time the prophecy is completed it doesn't kill Vercike but only puts him into a deep slumber. Vercike says that Cain told him to meet him into the inner sanctum before he died so he wants to go there with Ken and Agia while they fake fulfilling the prophecy - Vercike doesn't remember how Cain died.
Agia was put through hell by the Church through his whole life and told that the only way he could die, and therefore escape this hell, was by fulfilling the prophecy but lately, after falling deeply in love with Ken, he is starting to believe there may be hope for them both and it seems he doesn't want to fulfil the prophecy as asked by the Church anymore.
Ken was bitten by Vercike at the beginning of the story and therefore put through a curse that would kill him if he didn't stay with Agia (or Vercike for that matter but Agia got to him first). He's very deeply in love with Agia too but didn't want to go to the inner sanctum and fulfil the prophecy until very recent chapters because they now believe they may fulfil it in the right way and right all the wrongs. The curse on him has been lifted but he still chose to stay with Agia which is part of the reason Agia has regained hope, and since then he gets visions from Cain's life but it is still all very mysterious and the key to the plot almost certainly reside in Cain's memories (though we're getting weird vibes in the last few chapters from Cain but this part is just speculation from what we see).
So I tried to be as brief as possible, I hope this helped, good luck for the rest of the story (I think we're very close to the end now)!
Guys i cannot understand this bl for the life of me can someone please recap the whole thing ik im asking for alot but i beg. I tried rereading the whole thing but i cant and thats not including the breaks i keep taking please help.