@KriegGuardsman The little romance this manhwha has has a bit of a philosophical feel to it, but it's not the main focus. It's predominantly a shounen-style battle manhwha, and a pretty good one at that.
@Archiver My theory is that he was revived a second time, possibly warping or damaging his soul, making him forget about being a demon lord. It could also explain why the spirit possession gave him a debuff as well.