After My Sanity Hit Zero, I Became Invincible

The moment he awoke from the darkness, Nan Mingsui had lost all his memories. Only a voice that seemed to come from primordial times echoed in his mind, urging him to search, to find the person he had lost... Each time he dreamed, he returned to the underwater base where it had all begun. Seven colleagues from different places would guide him as he searched for his memories and for the person he was so obsessed with finding. He had thought these memories would be about an ordinary time working and getting along with ordinary people. He never expected things to start veering in a bizarre direction. A massive shadow occasionally appeared beyond the porthole. A humanoid creature with dull green scales flashed past. A mysterious box sent from the mainland for research. An ancient book covered in strange characters. His colleagues' mental states grew increasingly peculiar. In the darkness, crazed believers murmured in obscure tones. Deformed creatures escaped from the out-of-control laboratory. Terrifying, hideous purple spiders wandered through the darkness. Everything was dragged into a vortex of madness and distortion. Before the situation went completely out of control, they decided to return to the mainland and blow the place up. But the final message from the mainland left them frozen with dread. [We sent only seven people. Why is there an eighth?] The nonexistent eighth person might be the source of all the chaos and disorder. Fear, panic, suspicion, doubt, resentment, hatred, and slaughter, until blood soaked this deep-sea island they could not escape. At last, as everything came to an end, Nan Mingsui sat in the control room, surrounded by piles of monster corpses. His memories had reached their conclusion, and he was about to meet the person he had searched for so long. Monsters roared madly outside the door. A figure walked in, with a face he knew well. "What an unexpected outcome. So it was you." Nan Mingsui stared at him, etching his face deeply into his memory. In the man's eyes was a frenzied, twisted love. Sighing, or perhaps snickering, the young man opened his arms as if to embrace him. [You caught me. Too bad we're going to die together.] Intense love shimmered in his eyes amid the flashing light. "Is that so? What a pity this is how it ends. But it should all be over now." With a sigh, Nan Mingsui pressed the control button in his hand. The young man held Nan Mingsui tightly, smiling sweetly as madness and devotion bloomed amid blood and flames. [Let's meet again in hell, my god.] Nan Mingsui held him just as tightly, light flickering in his eyes. "No. This is only the beginning." Reader's Guide 1. Written on a whim, with an imagination free to run wild. Point out any plot holes and I'll try to patch them up. 2. Set in a fictional world, with an effort to make the worldbuilding plausible. Feel free to point out any issues. Reasonable suggestions are welcome. 3. The pairing is set. The romance develops slowly. 4. An unconventional romance. Theme: World peace