Kiyonori Yakumo is the devoted boyfriend of Hina Saotome, maintaining their relationship before and throughout her incarceration. He firmly believes in her innocence concerning the embezzlement charges that resulted in her imprisonment. Yakumo consistently visits Hina in prison, offering crucial emotional support despite the prison's restrictive environment, all while remaining completely unaware of the abuse inflicted upon her by prison guard Aki Myojin during those visits. Determined to free Hina, Yakumo actively collaborates with her to devise an escape plan, leveraging his outside access to coordinate their efforts. This plan specifically involves utilizing the prison's air vent system as an escape route. However, their attempt fails when Myojin discovers and intercepts Hina, leading to her recapture and severe punishment. Consequently, Hina's prison sentence is extended, and her visitation privileges are revoked, abruptly severing all direct contact between Yakumo and Hina. Yakumo embodies Hina's vital connection to her life beyond the prison walls and stands in stark contrast to the oppressive relationships she faces within the system. His forced absence following the revocation of visitation rights significantly deepens Hina's isolation and increases her vulnerability to Myojin's control.