The story begins with a male office worker, recently deceased after a truck accident, finding himself in a pure white void. He overhears a conversation between an old man and a woman, where the woman, tired of life, suggests the old man return the protagonist in her place. The protagonist, given a choice to live, agrees. He awakens in an unfamiliar room, discovering he has been reincarnated into a young woman's body. His initial shock and anger at this transformation are compounded when he realizes a timid 2-3 year old girl, Saki, is watching him.
The protagonist quickly learns he is now Saki's guardian. He discovers the apartment is filled with expensive brand items but no food, only beer, leading him to believe the previous occupant (whose body he now inhabits) was neglectful. Finding a significant sum of money, he immediately prioritizes Saki's hunger, taking her to a family restaurant. Saki, initially wary and silent, is overjoyed by her first proper meal, a simple omurice, and smiles genuinely for the first time, deeply moving the protagonist.
During a subsequent supermarket trip, the protagonist, now identifying as "Mika" (the name on the phone), notices Saki's suppressed desire for an anime toy. He realizes Saki has been taught not to be selfish, reinforcing his determination to provide her with a loving environment. A major emotional turning point occurs when Mika discovers, through an unsent email on the phone, Saki's tragic past: her parents (Mika's brother and his wife) died in a car accident, and Mika was her last resort after other family members refused to take her in. Overwhelmed with sadness and anger at the family's neglect, Mika embraces Saki, and they share a tearful moment, solidifying their bond. Mika vows to protect Saki and ensure her happiness.
Mika, despite struggling with her new female identity and pronouns (like accidentally using "ore" instead of "watashi"), fully embraces her role as Saki's guardian. She cooks homemade meals, contrasting with Saki's past experience of only "bento" (implying no home cooking). Mika also discovers her predecessor, Mika, was unemployed after a dramatic exit from her job (swinging a wig at her boss). Realizing Saki's inheritance should be preserved, Mika secures a remote call center job to support them. As Saki grows more comfortable, she becomes more affectionate, even developing a cute habit of proudly stating her age. The chapters conclude with Mika, now a devoted mother figure, finding joy in Saki's simple happiness, having transformed from a confused salaryman to a committed guardian, navigating the challenges of her new life and body.
