High school student Morinaga Kokoa has a secret crush on the boy she sees every morning on the train: Shinonome Banri, known school-wide as the perfect prince for his striking looks, sharp intellect, and flawless demeanor. But Banri is also famously cold and misanthropic, never smiling and keeping everyone at a distance. One day, Kokoa falls asleep on the train and wakes up on Banri’s lap, mortified. Shortly after, she witnesses him smile for the first time when he rescues her from a group of thugs, and she falls head over heels.

Kokoa’s earnest, puppy-like nature slowly chips away at Banri’s icy exterior. He eventually proposes they start a fake relationship—his motivation stems from a complicated family situation involving a stepmother he desperately wants to protect due to a heart condition. Kokoa agrees, hoping to win his genuine affection. As they spend more time together, Banri’s guarded heart begins to thaw, and he finds himself drawn to Kokoa’s selfless honesty.

Their budding romance is tested by several obstacles. Banri’s karate club friends, a group of seven handsome boys, take an interest in Kokoa, making Banri jealous. A bespectacled rival named Yotsuya develops genuine feelings for Kokoa and openly challenges Banri. During a summer festival, Yotsuya makes a bold move, forcing Banri to confront his own possessiveness. Later, an unexpected sleepover leads to a moment of intimacy that deepens their bond.

The biggest crisis arrives when Banri’s stepmother, Mika—who runs an entertainment agency—demands that Banri end his relationship with Kokoa to focus on family obligations. Banri, still torn between his devotion to his stepmother and his growing love for Kokoa, abruptly breaks up with her. Heartbroken, Kokoa tries to move on, but Banri’s feelings prove too strong to suppress. He returns to her, determined to fight for their love, and they reconcile as a true couple.

The story concludes with Kokoa and Banri officially dating and navigating their first physical intimacy during a trip together. The manga also includes additional one-shot stories, such as Oyasumi no Chuu wa Kuchibiru ni Shite. and Spicy Boy☆. Throughout the series, the central theme explores whether a shy, open-hearted girl and a moody, emotionally withdrawn boy can truly grasp and hold onto love.