Dunno why I suddenly thought about this one, but its started to bug me so I want to reread it so I can get it out of my head. From what I can remember, The basic premise is that the hero's sword is an evil one. Whenever the hero failed to kill the Maou, the sword would kill the hero. Then the Maou would constantly try to stop and warn the heroes that came after him. When one of them believed his story, the sword killed the hero anyway. After a time skip, another hero appears and finds the Maou depressed to the point where he didn't even look up from the floor when she walked into his castle. Then after giving her the same 'if you don't leave, you will die.' speech, he notices she doesn't have the sword with her. After asking, he found out that she doesn't have it because "The sword didn't think I was worthy enough to be a hero"(or something along those lines) Then for some reason, she starts to live with the demon king (This is the part that pisses me off because I can't remember why) Does this info ring a bell to anyone? its been a while since I read it, so there should be at least one other person who remembers this novel. I'm fairly confident that it had a 'meh' rating. (probably why I stopped reading it in the first place)
anyway i found it but next time try searching for it yourself first before asking :3 https://www.novelupdates.com/series/the-immortal-demon-king-and-the-impaired-hero/
I thought the title had something to do with the sword, and as such only searched for things similar to the title. But thanks!