Spoiler
why would they not stay together???!!!!!!
Right???
Wtf?! My poor tears is facepalming it's phantom hands
WHAT????? ALL MY EMOTIONS ON THIS STORY ONLY FOR IT TO BE LIKE THAT??!?!?!? F OFFFFFF
maybe they'll change it in the manga?? I've seen some do that
They better change it cuz it's not fair! Every movie, series or manga I've been watching and reading this month all ended up either having bittersweet ending, bad ending or a fucking cliffhanger
The demon king, aka ML, is actually destined to die because he no longer has the power to take in the excess mana that's polluting the world. If he doesn't take in the excess mana that's polluting the world, more monsters will come out and the world will go to ruins. Because he loves and treasures our MC, he banishes her back to their house and rids her of her memories, at the same time allowing her to turn back to her adult self, because he doesn't want her to save him, and make her feel sad or angry. The MC, after finding out, goes to save him even though she still has no recollection of him, up until the final end when she finally convinces him to not die as she is able to make tools that can save the world, something that he did not know because MC did not want to make the same mistake she did in her previous life. The two manage to avoid the death flag via the MC creating tools to absorb excess mana and the world is saved. The two live happily together, although their journey here seperates. ML becomes a teacher to teach children how to control their mana, and MC goes around the world creating this tools to save the world.
I got this off of the novel spoilers website, so I do not know anything else I am sorry