Tetsuo Amano works as a train conductor for the Kankyuu Railroad company on his hometown's Momokawa Line. He feels a deep attachment to the line, knowing its potential closure would threaten the town's survival by accelerating population decline and youth outmigration due to scarce local jobs. When signs point to the train operation becoming financially unsustainable, he joins forces with colleagues Makoto and Inoue to devise an unconventional plan. This strategy transforms late-night trains into venues catering to men seeking intimate encounters, leveraging anonymous train travel as a business model.

Tetsuo draws on his own past experiences as a former perpetrator, operating under a self-imposed ethical code that prioritizes mutual enjoyment and rejects non-consensual advances, which he despises. He possesses notable technical skill, particularly with his fingers, capable of eliciting willing participation. Using this ability, he identifies women potentially open to further group encounters within his specialized train services. While acknowledging the venture's moral ambiguity, he rationalizes it as necessary. A significant personal concern is the potential disapproval of his childhood friend Sana; he worries how she would react if she discovered his activities and whether he could face her afterward.