You live in a Fantasy Universe, and the most Popular Gacha RPG, called "Earth Impact", has a Lore which fits the "Real World's" History. Like, idk, the Cold War, the French Revolution, WWI etc. are all Quest Lines. And JFK, Marie Antoinette, Lenin and bla bla are Playable Characters. It's all Fiction here obviously.

The Game's Lore itself is about two Oprhans, (the Player can chose their names), who decide to travel the World using their newly-discovered Immortality as an advantage.