Unpei Mochizuki is in his second year as an employee at a machine parts wholesaler when a costly mistake at work leaves him reeling, desperate to escape to a place where no one knows his name. He gets into his car and drives, pulling over at a roadside stop where his life takes an unexpected turn. There he meets Tsugumi Nagisa, a picture book author with a youthful face and glasses who lives a nomadic life, traveling the country in her car with her dog as her only companion.

Intrigued by her unconventional lifestyle, Unpei joins Tsugumi on the road. Together, they begin a free-spirited journey across Japan, sleeping in their cars and following no set schedule. The narrative follows them as they drift from one scenic location to another, exploring the emotional and psychological landscapes of leaving behind a conventional, but unfulfilling, life. Unpei, burdened by his recent professional failure and the pressure of societal expectations, slowly learns to embrace the slow, deliberate pace of Tsugumis world. In contrast, Tsugumi, who embodies the migratory bird of the title, continues her search for inspiration and connection on the open road.

The manga explores their growing bond through quiet, everyday moments. The story is structured around the places they visit and the people they meet, allowing for a series of reflective vignettes that focus on healing, self-discovery, and the simple beauty of transient encounters. After serializing from October 2019, the manga went on a four-year hiatus following the release of its third volume in September 2021. It resumed publication in July 2024, with an anime television adaptation announced and set to premiere in 2027.