Kumi Kumakura receives a set of five special teddy bears handmade by her deceased mother, with instructions to give them to people who become important to her. Hoping for a fresh start, she transfers to a new high school, but her anxiety leads her to scout the campus the day before classes begin. There she meets Hyo Kakizono, a handsome and surprisingly kind boy who gives her a personal tour. Overwhelmed by his gentleness, Kumi experiences her first love and gives him her first kiss, also entrusting him with one of her precious teddy bears as a symbol of her feelings.

Her romantic fantasy shatters on her first official day when she discovers Hyo is not only her classmate but the school's most notorious playboy, famous for casually kissing many girls. Seeing him surrounded by other girls, she feels betrayed and declares she will hate him forever. However, Hyo surprisingly does not treat her as just another fling, and despite his reputation, he finds himself genuinely falling for Kumi’s sincerity and innocence. This creates the central conflict of the series, serialized in Sho-Comi magazine from August 2010 to December 2012 and collected into ten volumes. Kumi, a shy and reserved girl with a painful past, struggles to trust the words of a known womanizer. Hyo, who has always had everything easy because of his looks, must actively fight for Kumi’s trust and prove he can be faithful, a role reversal that distinguishes him from typical "bad boy" archetypes.

Their toxic and complicated relationship unfolds through notable narrative arcs driven by Kumi’s insecurity and Hyo’s past mistakes. A major turning point occurs when a specific event causes Kumi to distance herself from Hyo, leading to a rare moment where she demonstrates greater maturity. Hyo, meanwhile, struggles with the fear that his own dark past will ultimately destroy the fragile Kumi, sometimes leading him to hide his true feelings to protect her. The story also explores Kumi’s friendship with an outcast girl named Kanna Ogami, who becomes entangled in the romance, as well as the introduction of rival male characters like Tatsuki Hiyoshi and Chihaya Izumi, who add further complications to their love triangle. Throughout the manga, the five teddy bears left by Kumi’s mother serve as a recurring emotional motif, representing the bonds of friendship and love she forms.