okay first I need to move a little backward so you won't be confused by the future event (honestly, the manga skipped a lot of content, but I will only mention the
one of the witch's subordinate octo (demon who try to abduct Vernall in the past) was out of witch's lair to find a pray, he find one girl who delusional herself as Erise, Octo use that girl and force her to claimed herself as a witch to lure out Erise from academy, Octo also kidnaped few of the students to be a hostage, one of them is Eterna, Erise successfully intercept and prevent Octo to advance its plan, but during the commotion, the poisonous flower that made a delutional girl lost her mind fall down and lay in front of Eterna, she fall under the delusion and went mad, awaken her saint power, Erise and Vernall who join her later able to claim Erise down,
after the event, Eternal confessed to Vernall, but she knew well who Vernall looked up to, so she said not to worry or to be bothered by her, somewhat sad chapter...
later Leila commented that Eterna's power was so identical to the saint that she may have mistaken Eterna to be the saint if Elrise wasn't there, as we saw in the manga
okay, now onto Alfrea, first thing first, MANGAKA NERFED HER BOOBS, in the novel, it descripted that Alfrea's boob is melon big! damn it mangaka!
anyway, sad that mangaka skipped a funny part where Alfrea acted so childish and Propheter roasted her harshly lol, the onlooker student who came along has the image of the legendary first saint Alfrea brutality shattered lol, after that they bought Alfrea back, Elrise cooked her some earth dish and she said the famous phrase 'please be my wife' to Elrise lmao
after the special training, Elrise sneaked out of her room for a walk and found Vernal. he confronted Elrise with a clue he got, asking if she was really a saint. Elrise decides to tell him the truth that she's not. Vernal didn't bother by the fact and moved on to confess to Elrise, Elrise rejected him by telling the hidden truth that her lifespan would end soon and leave, leaving a shocked Vernal there
after that the narration shifts to Niito, he met with the author called 'turtle of Fiori' and he tell her about Elrise visiting him (altering a story that Niito himself is Elrise) and he learned that the author is actually someone who reincarnated on Earth from Fiori planet, and the event of the game was something that had already happened, and reveal the highest possible theory that the reason Niito can't see the info of the future event because the connection he has with Elrise that allow Elrise to visit him, so the world create a filter the content of future event so Niito can't spoil anything to Elrise, Niito come to understanding that his death that cause timeline breach has sent his soul to Fiori in the past which made the event on Fiori unfold very different from the original timeline, and Elrise coming to visit him is to retrieve the soul that didn't reincarnate properly
the narration shift back to Elrise, Vernal group go into underground where the witch reside, pretend to be lured by her, their aim is to depleted witch's mana while Elrise creating a barrier preventing the witch from regen mana, once witch's mana is depleted, Elrise and everyone concerned the witch and Alfrea seal the witch away, but the witch desire to die so strongly that the witch power inside Vernal react and that power trying to kill the witch, normally Elrise's pandent she gave Vernall back then could seal that power, but that pandent was slipped off during the fight, Elrise decide to kill the witch herself before the witch power inside vernal body could do
the dark power of the witch that lost its host will go to the person who killed the host, everyone was panick, but Elrise calm them down then revealing the shocking truth that she wasn't the saint, and the dark power that would enter her can't turn her into a witch, everyone fall into sarrow, especially Leila, she's so pitiful, after the dark power enter Elrise and died, Leila lost her mind and cry like no tomorrow, Elrise said, her death would bring happy ending, but at the moment, no one could feel joy or happiness at the slightest
edit*: forgot the mention: Elrise also revealed that Eternal was actually the real saint of this generation after she revealed herself
Elrise's funeral was held grandly at the state level. The news of her death caused shock to the entire world. The truth about her identity was revealed, yet no one despised her; on the contrary, they felt very bad that the huge responsibility was pushed to the ordinary girl. nobody dared to bury her body, so her body was sealed by Alfrea and enshrined instead
Afterward the dark power of the witch that lost its host materialized and became a huge titan, its aim was to destroy the world's light the light called Elrise, by destroy it, the hope of humanity will all be lost, the resistance was formed by the kingdom's knight and the saints, yet it's futile because that body could de-materialized when attacked and re-materialized when attack, the witch reach the temple where Elrise's body enshrined, Vernal tried to resist the best he can, but still can't do anything, right now all the hope seem to lost...
the pov shift to Elrise, she's back at the apartment, Niito showing her the scene of the titan witch trambled the town and people, finally they both come to the realization that they have been treated that world as if it was a game all along, and never see anyone as a being at all, Elrise too for the first time wish to do something but she can't because she already death, Niito offer his last ounch of his soul, if Elrise accept this soul, the soul of Niito will be completely merged with Elrise and he would die, but he doesn't care about it, so Elrise took that soul which would not give her much lifespan
back to Fiori, Elrise body resurrected and she confront the witch, right now Elrise soul was complete, her mana got many time stronger, finally she was able to defeat the witch with power of the light from the hearth of people, but her little lifespan she got from Niito soul was deplating, and she was about to die again, Propheter use that opportunity to appoint Elrise as a new Prophet, the the role of Prophet can be transfer only via appointment from the current Prophet to the new one, and the remaining lifespan of the previous Prophet would also transfer to the new Prophet, so Elrise got the remaining lifespan from Propheter which said it won't last long, probably a few handread years left (yeah, totally not long at all), and Propheter has died
after that mostly just a conclude chapter, Eterna develop a feeling to Vernal's dormmate, Vernal dropped out and embark on the journey to strengthen himself to be a man worthy enough for Elrise, Elrise decide to revive Alexia (the witch) as per her promise with the former head master, also since Elrise's influential right now was like a god to people in Fiori, she decided to flee and live in the forest she met Propheter, she brings Leila along since Leila would be really sad if she left her, with the power of Prophet, she can hear and see in the distance if she focus her mind, so she sometime helps the one in needs, really the great conclusion of the story
back to the author side, it was reveal that she is actually Propheter who reborn on Earth, after the battle ib Fiori, she tried to ask the producer about Niito, but apparently the identity of Niito was erased from existence, she didn't know why, but us reader understand that Niito now fully become one with Fiori planet, so his existence on earth can be erased as it should be all along,
that's basically the conclusion of the main story. There's the story when Elrise discovers the portal to Earth and meets with the author, but please read the novel if you want to see!