Married woman Aika is forced to commute by train every day after starting to help out at a factory run by her relatives. Once a victim of molestation, she had avoided crowded trains ever since—until now. Back in that familiar, suffocating environment, she trembles as lewd hands grope her thighs, slowly succumbing to waves of pleasure. Despite her flashy appearance, Aika is timid by nature, unable to resist the groping and passively accepting each assault. Torn between guilt toward her husband and lingering trauma from the past, the intense sensations surging through her body lead her toward unexpected ecstasy. Once again, she boards the packed train, ready to repeat this forbidden experience.