Office worker Eiko has led a quiet, ordinary life with no particular interest in cats. That changes when a friend persuades her to attend a pet adoption fair, where she locks eyes with a stray cat and instantly falls in love. Impulsively adopting the cat, whom she names Nacca, Eiko finds herself navigating a world of firsts: first feeding, first litter-box accident, first night of anxious waiting for the cat to come inside. As days pass, Nacca reveals a capacity to be a friend, a silent confidant, sometimes even a source of jealousy or comfort, blurring the line between pet and family member.

The story follows Eiko’s gradual adaptation to life with a cat and the small daily adventures they share. Nacca’s personality emerges through episodes: hiding, hunting a moth, getting drunk on catnip, disappearing for a night, and learning to trust. Just as Eiko settles into a rhythm, she meets a man who genuinely loves cats. Their relationship grows, and the presence of Nacca becomes a bridge between them. The arrival of this cat-loving boyfriend shifts Eiko’s solitary world into a new configuration, deepening her emotional connections and forcing her to reconsider what home and companionship mean.

Throughout the series, the narrative arc moves from Eiko’s initial inexperience and anxiety to a quiet confidence as a cat owner, then expands to include the dynamics of a three‑member household: Eiko, her boyfriend, and Nacca. The chapters are titled with single verbs that capture key moments—Lean In, Watch Over, Get Worried, Celebrate, Hunt, Get Drunk, Forget, Disappear, Get Jealous, Respond, Begin—each focusing on a small but meaningful incident that reveals the evolving bond between human and cat, and between the two humans. The setting remains firmly grounded in everyday Japanese urban life: a modest apartment, a workplace, a park, a vet’s clinic. The tone is warm, observational, and occasionally bittersweet, emphasizing the quiet transformations that come from sharing one’s life with an animal and from letting another person into that life.