Ten years ago, the Gates opened, bringing bloodthirsty demons into the world and stealing away Tanjiro Kamado's family, leaving his younger sister Nezuko trapped in a demonic, comatose curse. To pay for her life-support at the Ubuyashiki Association Hospital, sixteen-year-old Tanjiro works as an E-Rank Hunter, universally mocked as the "World's Weakest." But during a routine D-Rank raid, his party stumbles into a hidden Double Dungeon-a lethal trap designed by the Architect, Muzan Kibutsuji, to find the perfect human vessel. Left for dead on a sacrificial altar, Tanjiro expects the end. Instead, a voice echoes in his mind, and an ancient power long hidden from the Architect awakens within his shadow. The System has chosen its Player, and the hunt begins. This is my first fanfic of demon slayer x solo leveling. I don't own any of these characters Neither any of these two anime Solo Leveling and Demon Slayer they belongs to their respective authors.

Yukimura Kaidō lived as a ghost in his life-bullied for his feminine features, beaten until he lost an eye, and too afraid to fight back. He spent his days hiding behind a computer screen, finding courage only in the final seconds before a truck ended everything. Death should have been the end... Instead, he woke up in the Demon Slayer world. [Ding! Compatible transmission target detected. System binding initiated... Binding successful!] [Ding! Congratulations! Host has received: Body Enhancement Serum x1, Total Concentration Breathing: Constant, Dragon Breathing First Four Forms, and 100,000 Yen.]

Giyuu lay dying on his 25th birthday recounting all the good times he spent with his friends before and after the final battle with the demon king and his servants. Yet, as he takes his last breaths and finally finds solace in the life he's lived, he is mysteriously transported back a whole 8 years in the past. Now faced with a second opportunity to correct his mistakes and save the lives of those he felt indebted to, what would he do? -Certain character ages may be changed for the sake of the story (specific birthdays will be explained later). -Manga spoilers (why would anyone read a fanfic about the end of the series if they didn't finish the story)