Having limited exposure to the opposite gender, Hanako feels overjoyed upon learning that Bara High, along with its dormitory, is introducing co-education. Yet, her elation is quickly dashed when she encounters Kakeru, the leading scholar at the all-boys school. Although he looks charming at first, Kakeru's real intentions come to light when he insists on sharing a room with Hanako. Now, Hanako must determine how to handle this unforeseen predicament.
On the second day of the academic year, Hanako wakes up to find graffiti scrawled all over her bed. Furious and frustrated, she reports the incident to the dorm supervisor, but he does not take any action, informing her that it is her responsibility to remove the graffiti. Hanako gets to work, scrubbing and wiping every inch of the bed, but the ink stays put.
As she walks down the hallways, Hanako sees similar graffiti on other people's doors and beds. Her desperation increases, but instead of surrendering, she decides to take charge. With the help of her friends, Hanako organizes a secret task force to clear the dormitory of the graffiti. They work tirelessly, erasing the marks with water, soap, and even nail polish remover.
After days of effort, the graffiti is gone, and the dormitory finally becomes the welcoming and pleasant environment that Hanako had hoped for. Her boldness and perseverance inspire her roommates, who begin to emulate her actions. As for Kakeru, Hanako decides to take a chance on him, realizing that his request to share a room may have arisen from his own insecurities. Together, they begin to navigate the ups and downs of co-education, discovering newfound maturity and understanding.
