The story begins on a rainy night with the protagonist, Matsutomo Yuji, returning home late from work. He encounters his neighbor, Saotome Mio, standing in the hallway, drenched and distressed. Mio has forgotten her keys at her business trip destination, which is three hours away, and her phone and wallet were in the same bag. Unable to contact anyone or get home, she is stranded. Yuji, despite his initial surprise and reluctance to lend money, offers his assistance.
Mio reveals that the documents she needs for an important work presentation are inside her apartment, and without them, her company might collapse. Faced with this crisis, Yuji devises a daring plan: he will climb over the balcony from his apartment to hers, break a window, and open the door from the inside. After a tense crossing, Yuji successfully enters Mio's apartment, which is surprisingly cluttered with cardboard boxes and empty plastic bottles, giving it a somewhat neglected appearance. He opens the door for Mio, who is overwhelmed by the state of her home. Yuji offers her a comforting "Welcome home," which deeply touches Mio, who reveals she hasn't heard it in ten years. She then proposes to hire Yuji as her "Welcome Home Manager" for thirty thousand yen a month, a proposition that initially stuns him due to her high salary and the unusual nature of the job.
The next morning, Yuji oversleeps and is fired by his boss. However, the company president calls, informing him that he has been headhunted and is now employed by Mio's company. Yuji is then summoned by Mio, who confirms her intention to hire him. He accepts the job, which involves saying "Welcome home" to her. His new role begins immediately, with his first task being to prepare dinner for Mio.
Over the following week, Yuji learns more about Mio. She is a capable marketing professional who works for a successful, albeit small, company. Despite her professional competence, she struggles with social interaction and loneliness in her personal life. Yuji also discovers her peculiar sense of hygiene, where she meticulously disposes of perishable waste but leaves empty bottles and unopened mail scattered around. He begins to clean her apartment as part of his duties.
One evening, while preparing dinner, Yuji encounters a cockroach in the kitchen, causing him immense distress. Mio, who is in her bedroom changing, bursts out in a panic, revealing she is terrified of them. In the ensuing chaos, Yuji, despite his own fear, bravely confronts the cockroach, protecting Mio.
The following Saturday, Yuji, now on his day off, is invited by Mio to go shopping for a stuffed animal. She offers him ten thousand yen as "holiday work pay," revealing her desire to buy a new stuffed animal to accompany her existing one, "Fuu-chan." They visit a specialty store, where Yuji also ends up buying a stuffed octopus. Mio then suggests they visit a game center, a place from Yuji's past. There, they find a worn-out stuffed cat, which Mio insists on adopting, despite its poor condition. Yuji, witnessing Mio's determination, helps her win it from the crane game.
The narrative concludes with Yuji reflecting on the peculiar nature of his new job and his employer, acknowledging the strange circumstances that brought them together.
