The old man in the story is Manager of Video Shop Gokuraku, Japan Branch. His real name is unknown. Despite the term 'Manager', he belongs to the lower echelon of the Gokuraku and basically manages the 'rental system' in the video shop. He has some specialized knowledge in the field of Video Girl Engineering and helps him employer, Rolex, in development and maintenance of equipment. In the series, he is the only 'normal human' employee working for Gokuraku.

(Source: Video Girl Ai Manga and Anime Resources)