This series has been going on for nearly 70 chapters now, and it's pretty good, pretty well-written, and with a cool premise. Even still, I feel like there's just some spark that it's edging close to, but not yet reaching, that'd make it a hit. I don't know if it's too late now with how long it's been going on, my instinct is that with a proper consistent overarching antagonistic force (beyond the demon king), or some way of making the journey itself feel more substantial or higher-stakes, even if the flashbacks are pretty good. Right now it kinda feels like we get a lot of lore, then the final battle with whatever form the demon king is, then repeat.