Souta Minori is an ordinary high school student whose daily commute on the train is brightened by the sight of a stunning girl from a neighboring school. With her pure white hair, striking blue eyes, and an aloof demeanor that repels all advances, she is known as the Ice Princess, Nagi Shinonome. Souta admires her from a distance, content to keep his ordinary life unchanged, until one morning he witnesses her being molested on the crowded train. Gathering his courage, Souta intervenes and rescues her when no one else will.

The next day, Souta expects to return to his routine, but Nagi surprises him by approaching him directly. After thanking him for his help, she makes an unusual request born from her sorrow and isolation. With no friends and a deep distrust of others, she asks him to simply stay by her side during their train rides. Unable to ignore the loneliness in her voice, Souta accepts, becoming her first and only friend. This tentative agreement sets the stage for an awkward but deepening relationship between a boy who never sought the spotlight and a girl whose cold exterior begins to thaw into someone sweet and possessive only for him.

The story is set in a contemporary Japanese high school environment, following the daily lives of Souta and Nagi as they navigate the uncertain ground between friendship and romance. As they spend more time together, Nagi becomes increasingly attached, showing a clingy and affectionate side that she hides from everyone else. Souta, in turn, finds his ordinary life upended by her unwavering attention. Their relationship progresses from shared train rides to cooking together and other intimate activities, all while maintaining the fragile label of friends. An outgoing best friend and his girlfriend provide a contrasting dynamic and occasional comic relief.

The narrative is largely a sweet, low-stakes romance focused on gradual intimacy and mutual affection. Early chapters establish their arrangement and Nagi's swift emotional attachment, avoiding a slow thaw in favor of a more immediate connection. However, the story introduces a notable dramatic arc around chapter 35 when an arranged marriage proposal from Nagis family emerges as a source of conflict, challenging the bond the two have built. This plot point introduces tension but is resolved relatively quickly, allowing the story to return to its core focus on the fluffy and progressing relationship between Souta and Nagi. The manga adaptation began serialization in July 2024, based on the original light novel series.