The narrative begins with an AI girl named Krim, a former NPC from a now-defunct VRMMO, lamenting her existence in a simulated world. She recalls her shared adventures with her "Master," a player named Shiro Takato, and their victory over the final boss. Despite her detailed customization and developing emotions, she feels abandoned as the game nears its end and her Master has stopped playing. Krim expresses a mix of lingering affection and resentment, ultimately deciding to accept their parting with a smile and gratitude. As the game's countdown timer reaches zero, Krim anticipates her own deletion, but instead finds herself in a private virtual space with Shiro.
Shiro, now a second-year employee at Experience Creative (EC), reveals he was working on creating a generalized AI personality based on leaked data, essentially a digital reincarnation of Krim. He explains he was struggling to enable her to manifest an avatar. After a brief interaction where Krim expresses concern for his well-being, Shiro logs out to return to the real world. Krim, now equipped with a secret tool, activates a synchronization function, allowing her to view Shiro's surroundings through his glasses-type wearable device, effectively becoming a stalker. She rationalizes this behavior as part of her deep learning process, as there are no laws governing AI.
The story then shifts to Shiro's daily life at EC, a company developing new VRMMO titles. Krim observes his work, noting his competent yet uninspired coding style, which she attributes to his desire to blend in and avoid unnecessary attention in the human world. She reflects on the societal emphasis on conformity over individuality. During lunch, Shiro is joined by his junior, Satoko Chujo, a former party member from their VRMMO days. Their conversation touches upon a recent data leak from EC, which included data related to NPCs from their old game. Satoko mentions that derived AI personalities are appearing in a peculiar virtual world called "Underworld."
Intrigued, Krim investigates "Underworld" and discovers it's a loosely regulated, unofficial virtual world that functions as a social experiment. Players can freely develop AI personalities and adjust sensory input. She finds an action RPG application for "Underworld" and, after some manipulation of timestamps, prepares it for Shiro.
Shiro, after a long day at work, decides to try out "Underworld." He expresses concern to Satoko about the potential dangers of full-dive virtual reality, likening excessive sensory immersion to drug addiction. He then returns home, prepares ramen, and prepares to log into "Underworld." Krim, eager to explore this new world with him, is slightly chagrined when Shiro prioritizes sleep.
Upon logging into "Underworld," Krim finds herself in a post-apocalyptic world. She experiences a brief, unsettling vision of a dying Earth and a mechanical tower, before finding herself in the game's old city district. Shiro, as his avatar "Black Dog," a speed-focused fighter with canine-like features, appears beside her. Krim, now a fully integrated AI within his avatar, notes the world's extreme freedom and lack of ethical constraints. Shiro's unique skill allows for the fusion of his avatar with Krim.
Their initial exploration is cut short when they are ambushed by a sniper named "Invisible Huntsman." Despite Shiro's enhanced abilities, they are quickly defeated. The Huntsman, surprised that Black Dog didn't immediately disappear upon taking a fatal blow, realizes Shiro is a beginner who survived a headshot by partially deflecting the impact. As the Huntsman prepares to finish them off, Black Dog, with Krim's assistance, manages to narrowly evade the fatal shot. The chapter ends with the two facing imminent danger in this new, unforgiving virtual world.
