Sixteen-year-old Shinra Kobayashi lives alone in a tiny four-and-a-half-tatami mat apartment, having been abandoned by her mother who moves from man to man without concern for her daughter. With no parents, no friends, and barely enough money to survive, Shinra has become jaded and hardened, viewing youth, romance, and even small luxuries like makeup or Starbucks as unaffordable dreams. She works a part-time job where she tolerates harassment from her manager because she desperately needs the income.

Her solitary life takes an unexpected turn when she is spotted eating food off the ground by Rai, one of the three most popular, handsome, and wealthy boys at her school. Fascinated by her circumstances, Rai bluntly tells her he wants to be friends. Shinra, offended and suspicious of his motives, rejects him, but Rai persists alongside his two best friends, the calm and gentle Kanan and the energetic Hyakkei. Initially viewing their interest as a mere curiosity or a chance to take her in as a rich boy's pet, Shinra eventually decides to enter a calculated partnership with them as a way to escape her desperate situation.

As the story progresses, the boys work to insert themselves into Shinra's life, though their privileged upbringings prevent them from truly understanding the depths of her struggles. The narrative follows a dark and dramatic cycle where Shinra faces new hardships just as she begins to find stability. In volume two, desperate for money, she attempts sugar dating and is nearly assaulted in a hotel room, forcing Rai to rescue her. He later opens up about his own complicated upbringing, bringing them slightly closer. Volume three sees Shinra's mother suddenly return home, and Hyakkei confesses his feelings for the first time, creating a love triangle when Shinra finds herself unable to stop thinking about Rai.

After suffering sexual harassment from her mother's new boyfriend, Shinra loses her place at home and is taken in by Kanan. She later becomes a tutor for Kanan's younger sister, Seina, and tries to help mend the strained relationship between the siblings. Tragedy strikes again when Shinra's apartment is burned down, forcing her to stay with Rai while the arsonist is investigated. She then becomes entangled with a mysterious man named Fuya, who shows her a scar on his stomach where his mother stabbed him. Shinra, who has been repeatedly betrayed by her own mother, feels a deep sympathy for him. However, rumors begin to circulate that she is living with Kanan, forcing her to leave his apartment. She turns to Fuya for help and begins living in a business hotel, a decision that places her in grave danger. When her betrayal of Fuya is discovered, he kidnaps her. The three boys rush to save her, but Shinra finds herself resonating with the wounded Fuya, who shares her pain. The series explores heavy themes including child neglect, poverty, sexual harassment, and the struggle to trust others, depicting how deeply trauma can shape a person while Shinra perseveres in her fight for a better life.