There is a fanfiction called 'Operation: Redemption'. It's about a disgraced operator getting a chance to redeem himself. It has great character development and intense action scenes, which makes it very engaging.
Rainbow Six Siege does feature a story mode. However, it's not as extensive as in some other games. The focus is more on multiplayer, but the story mode provides some background and context to the game's universe.
Rainbow Six Siege multiplayer has a deep story. It's about intense battles between teams, each trying to outsmart and outperform the other. The game constantly updates with new operators and content to keep the experience fresh and engaging.