Matsutomo, a salaryman in a demanding company, faces endless tasks dumped on him by his forgetful chief. Known as Matsumoto to all, he crosses paths with his enigmatic neighbor, Saotome-san, one fateful night. Discovering she's left crucial belongings at a distant supplier's, including vital documents locked in her inaccessible apartment, Matsutomo steps in to assist. Grateful for his aid, Saotome-san extends an unexpected offer, altering Matsutomo's path in ways unforeseen.