Everyone Regressed Except Me

Story:

Lee Hwayoon, one of the few players who entered the last dungeon, finds himself among the players who have returned to the past with their memories intact. [System Error!] [Searching for a special skill…] [Special skill search completed.] [Please check the status window.] [Butterfly Effect, Level 1] [The only person who hasn't regressed will be awarded bonus points for your actions changing the future.]