Kazuki Tanaka, a typical young adult living in modern-day Japan, leads a mundane life working a part-time job and immersing himself in his hobbies. Little does he know that his life is about to take a dramatic turn when he steps into his apartment after a long day. Complaining about the monotony of his job, Kazuki picks up his bag, which contains his laptop and other groceries. As he opens the door to his apartment and flicks on the lights, he briefly closes his eyes, expecting the familiar sight of his living room. But when Kazuki opens his eyes, he is no longer in his small apartment. Instead, he finds himself standing in a vast space bathed in daylight, with a grand mansion looming before him.