Masahiro Hino is a 25-year-old deliveryman with brown hair and grey eyes, standing 1.76 meters tall and weighing 69 kilograms. He previously attended college with Nanami Honda, where he carried unspoken romantic feelings for her—a regret that lingers from his past. During a routine delivery to her residence, he inadvertently uncovers Nanami's predicament: she is sexually blackmailed by Genji Kamata, who possesses compromising footage of her. Driven by his unresolved emotions, Masahiro feels compelled to liberate her from this coercion.

However, his intervention takes an unexpected turn when he becomes sexually entangled with Nanami himself. This new affair compounds her existing secrecy, as Nanami fiercely conceals it from her husband, Shuuichi Honda, viewing it as a separate betrayal beyond the initial blackmail.