After graduating high school, Suzukaze Aoba joins Eagle Jump, the game company that developed Fairies Story, the game she obsessed over as a kid. On her first day as a working member of society, Aoba heads to work swaying in a packed, morning rush hour train. She manages to get to the office building all right but hesitates, wondering if it was really okay for her to take that last step and go inside. That's when a senior member of staff, Toyama Rin, shows up at work and safely leads Aoba inside the offices of Eagle Jump.
In the near future, a Virtual Reality Massive Multiplayer Online Role-Playing Game (VRMMORPG) called Sword Art Online has been released where players control their avatars with their bodies using a piece of technology called Nerve Gear. One day, players discover they cannot log out, as the game creator is holding them captive unless they reach the 100th floor of the game's tower and defeat the final boss. However, if they die in the game, they die in real life. Their struggle for survival starts now...
Awakening her dormant abilities as a devil one day, Yuuko Yoshida aka Shadow Mistress Yuuko, is entrusted with the mission to defeat the Light clan's shrine maiden, a magical girl, by her ancestor Lilith. Yuuko meets magical girl Momo Chiyoda through her classmate Anri Sada, and challenges her to a duel, but loses quickly due to her lack of strength. Since then, Yuuko has struggled with her role as a devil and her duel with Momo, and borrowed help from her regularly. However, by a strange coincidence, Yuuko also weakens Momo by taking away her power to cooperate in protecting the peace of Tama city.
