Paradox: Sign-In Across Two Worlds

Neolan met his demise at the hands of an Unknown Demon, which pierced and crushed his heart, filling his fading consciousness with regret and fury for failing to save anyone he cherished, as well as the world he had fought to protect until his last breath. However, what follows his death astounds him deeply. He finds himself reincarnated in a body that is not his own, in a completely different realm where Cultivation is a reality, and the route to gaining strength diverges entirely from what he once knew. Luckily, he awakens a stereotypical Sign-In system referred to as the Paradox Sign-In System, which operates under a straightforward rule: Sign-In once every 24 hours to receive a completely random reward. Armed with the memories of his past life and the System now at his disposal, Neolan starts to adjust to this new environment while trying to comprehend what has transpired. Yet, he soon encounters something that should not exist in this world: Demons. The very Demons that had obliterated Earth. Before he can uncover the answers he seeks, his initial 24 hours in this new world come to an end. The System then presents a message that leaves him in shock. [24 hours have passed. Host will now be transferred to Earth.] At that moment, Neolan grasps the reality of the situation. He has not merely reincarnated in another world; he has also regressed in time across both worlds. - - -Extra tags: Cultivation | System | Transmigration | Reincarnation | Apocalypse | Overpowered Protagonist | Strong Protagonist | Multiple Worlds | Dual Systems | Sword master | Demons | Survival | R18 | Dimensions/Realms | Awakening | Regression [Warning: There will be explicit scenes in the future, read on your own terms, you can skip them if you want]