Tsuki 50-man Morattemo Ikigai no Nai Tonari no Oneesan ni 30-man de Yatowarete "Okaeri" tte Iu Oshigoto ga Tanoshii

Matsutomo is a salaryman at a black company who's being overworked to death by a chief who's a pro at dumping all his work on him. What's more, no one seems to remember his name and they all call him Matsumoto. One night, coming home late once more, he runs into his beautiful yet distant neighbor, Saotome-san. It seems that she had left her phone, wallet, and the apartment key in her bag at a supplier's place 3 hours away. And in the apartment she can no longer get into, she has some important documents that she must have for tomorrow's meeting! Ever a gentleman, Matsutomo helps her out, saving her from the predicament, and moved, she makes him an offer he never gets a chance to refuse. (Source: MangaDex)