Exceptis Vos

A semi-mystery love story of a guy's point of view. He's receiving a letter from his admirer and there was a weird word that was written in the bottom. First, he doesn't have any interest of finding his admirer but it creeps out that it looks like his admirer is kinda stalker. One day he didn't expect himself for receiving another letter and he become curious about his admirer's identity. He kinda used to receive it. What's the meaning of those weird words? Who is she?