Decades ago, the invincible hero and the almighty demon lord of the age met in battle for the final in a drawn out clash that shook every corner of the world. Days and nights passed as the land, sky and sea were seared in their battle colors before their duel ended in a blinding flash that saw their departure from the realm of man and demon alike. The new age is upon the land now and the new hero and demon lord are to arise once more to renew the cycle once more but this time it seems that only the demons see a new savior in this age.
Years pass and the dominion of the human empire has shrunk and splintered without a mighty hero to rally against. A prophecy spreads that the new hero will not be chosen by birth but a worthy soul shall take up the cause when the last hero's spirit finds them. The young are empowered by this and aspiring heroes train themselves up to be the one in the prophecy and to do their part in guarding the humans to significant success. This story centers around a pair of twins and the former hero.
It all starts in a village bordering demon territory where a pair of brothers are aiming for the title of hero themselves. One day they face off a pack of demons that prove to be too much for them but before they get turned into demon feed, a priestess of the light spirit saves them with magic. The boys thank her and lead her to their village where she is celebrated for her presence since they long thought that the temple had abandoned them. She tells them she is only passing through and will only be around for a few days as she must continue her travels but she will bless their land while she is here so she asks for a private house to stay in.
The villagers naturally compete for her attention but it is mainly the twins who get sizable portions of her time for training in magic. She's delighted to find that both have a natural talent for the craft so the village agrees to accede her time to them but she also makes sure to make time for the other strapping virile villagers she blesses in private at night in the house they provided for her.
One night, the twins make an exciting breakthrough in their magic training and rush to the priestess to show her their progress but are in for a shocking sight when they barge through the door. There were a pair of bodies naked and bare on the bedding and while one lay limp and unconscious, the other clearly belonged to that of a demon and shared a disturbingly familiar face. The irritated "priestess" attempts to cast magic on them but they regain their senses quickly enough to show the fruits of their labor and dispel her bewitching charm with a light barrier.
She's surprised to see their defense work so well, so much so that she forgets she was trying to erase their memories and happily rushes them in to hear more of their progress. The boys are too shaken to refuse but are somewhat assured that the demon woman in front of them is indeed the same priestess they've come to know over the past few days. Barely draped in her travelling hood for quick modesty, she surveys their current mastery over light to her excitement. The innocent lads awkwardly try to look past her nakedness and question her about her identity only for her blithely tell them that she's previous hero but now she's a travelling succubus that masquerades around as a priestess to find her successors.
The previous demon lord had used the last of his powers to curse him into her current form. It was difficult at first but time passed and she's come to very much like her "curse" and there weren't many downsides to having an eternally young body except for one in particular that stood out - a new hero couldn't be born while she lived. She's been enjoying her travels but responsibility weighed down on her so she came up with the prophecy to find a successor. The hero's blessing can be passed down by her will but there is a catch, the successor will also inherit her curse as well. She very glad that the boys came tonight since she was going to leave in the morning without candidates to walk away with but now she's got two promising boys to meet her needs.