In a near-future Japan where VRSN (Virtual Reality Social Network) services have become commonplace, a high school girl named Kanata accidentally finds herself trapped inside a virtual world that meticulously recreates an old civilization. This immersive space is not an empty game lobby but a lived-in environment populated by local people going about their daily lives. As Kanata interacts with the inhabitants, she gradually adapts to the rhythms of this antique world, learning to navigate its customs and forming connections with the people she meets. Just as she begins to feel a sense of belonging, a familiar threat emerges: monsters from a video game she recognizes appear and begin attacking the peaceful citizens.

Faced with the danger closing in around her new friends, Kanata makes a critical decision to protect them. She chooses to sacrifice her own game data, the very currency of her existence and abilities within this space, in exchange for the safety of the people and a path back to the real world. Her plan succeeds, and she manages to return to her own reality. However, the experience carries an unexpected revelation. Upon her return, Kanata comes to understand that her journey was not merely a dive into a digital construct but a genuine voyage into the actual past, meaning she had traveled back in time. The central character is Kanata, whose voice is provided by actress Kanata Aikawa; her mother, a supporting character, is voiced by Mayumi Shintani. The narrative arc follows a clear trajectory from accidental entrapment and reluctant integration to heroic self-sacrifice and the stunning discovery that her virtual adventure was, in fact, a real historical event.