The story begins by introducing Satake Yashiro, a 29-year-old single man working as a workaholic at a major IT company. His life is consumed by his job, leading to poor eating habits and a lack of social life. He eventually collapses from overwork and malnutrition, causing his company to face public criticism and implement labor reforms. Although the work environment improves, Yashiro resigns. After a brief period of handling his work handover, he enters a period of recovery, dedicating himself to self-improvement through cooking, running, and studying stocks.
Two months later, during his morning routine, Yashiro is interrupted by a delivery person at his door. To his shock, the visitor is a man in black, wielding a carving knife. Yashiro attempts to defend himself using a self-taught martial art, managing to push the assailant towards the door. However, the attacker then produces a 3D-printed gun. Yashiro is shot in the chest and then fatally stabbed by his former superior, who blames Yashiro for ruining his life.
Yashiro awakens in a pure white space and encounters Inanna, a goddess of life, death, and reincarnation. Despite being informed of his death, Yashiro remains surprisingly calm, much to the goddess's bewilderment. He correctly deduces that he is being offered reincarnation into another world. However, Yashiro refuses, stating he wishes to rest and finds the prospect of adapting to a new world overwhelming after his previous life's exhaustion. He then surprisingly agrees to reincarnate if it's not into a new world, leading to a chaotic argument with the young goddess who is desperate to fulfill her reincarnation quota. Inanna forcefully sends him back to modern Japan as a baby.
Yashiro is reborn as Yashiro Makoto, a two-year-old boy in modern Japan, retaining his memories of his past life as Satake Yashiro. He finds himself in a world he knows but with a significant time rewind, placing him in his childhood. He lives with his single mother, Akari, who works hard to support them. Makoto, despite his infant body, possesses the intellect of his former adult self. He quickly adapts to his new life, charming his mother and her childhood friend, Totsuka Mio, and Mio's daughter, Suzuka. Makoto develops a deep affection for Suzuka, whom he views as an angel, and enjoys their time together, often acting as her protector. He also cherishes his time with his mother, Akari, appreciating her efforts and vowing to support her. The narrative highlights Makoto's unique perspective as an adult mind in a child's body, navigating daily life, his relationships with Suzuka and Mio, and his mother's struggles. He finds solace and joy in his new life, particularly through his interactions with Suzuka and his mother.
