Ryo Ishizuka is a young man studying to pass the accountant's examination while working a part-time job at a secondhand shop. He has secretly been in love with his older coworker, Yuzuki Tachibana, for months, finding emotional comfort in her kindness. When he finally gathers the courage to confess, he is rejected. Yuzuki is a widow and a single mother to her young son, Asahi. She tells Ryo that she is not simply a woman, but a mother first, and questions whether a part-timer like him could ever hope to support a child.

The story follows Ryo as he refuses to simply give up, instead choosing to truly understand Yuzuki's life and the weight of her responsibilities. The setting shifts between the characters' workplace, a recycle shop called ECOECO, and Yuzuki's home, where she also runs a small restaurant that her late husband had been planning to open. As Ryo becomes a part of their daily life, he forms an unexpected friendship with the bug-obsessed five-year-old Asahi.

The narrative focuses on the slow, realistic development of a relationship between two people at very different stages of life. Yuzuki is approaching her thirties and has closed herself off to the idea of romance, believing that dedicating every moment to her son and work is her only path. Ryo is naive but persistent, and his initial selfish crush gradually transforms into genuine empathy and respect as he witnesses her struggles. A significant early arc involves Ryo suffering from insomnia and exhaustion due to his grueling study and work schedule, which leads Yuzuki to care for him in a maternal way, blurring the lines of their relationship.

As the series progresses, major arcs explore Ryo proving his reliability to Yuzuki and those around her, including helping with childcare and her business. Concurrently, Yuzuki begins to confront her own fears and the loneliness she has suppressed since her husband's death. The story centers on the idea that both characters must learn to accept help and vulnerability. Ryo must mature into someone worthy of being a partner and a father figure, while Yuzuki must learn that she is allowed to want happiness for herself as well as for her son. The complete manga ran for four volumes, chronicling their journey from a workplace crush to the formation of a new family unit.