San Otonashi is one of the main protagonists of Eds + Vampires. She is a graduate from Youkai Academy and the former president of the Newspaper Club. She rarely speaks, which because her powers lay in voice, and carries around a sketch book to write on instead of talking to keep others safe. She was the one who taught Ginei Morioka how to use a camera and stopped him from fighting everyone in his first year. She now lives with Marin who found her after she had nowhere to go.
San is generally a very happy, pleasant and sweet girl. Though despite her youthful appearance, San is actually a very mature and tough character. Back when she was in Youkai Academy she was responsible for straightening out Ginei. Due to her shyness she doesn't, but her form of communication is by her notepad on whe she writes out her dialouge.
According to Ginei and Haiji, San was a truly fearsome fighter back when she was in Youkai Academy. Like Moka, San's notepad serves as her limiter for her powers. When she closes her notepad, she's serious about fighting. Her powers as a Siren are so great, that she was deemed a genius by Yokai Academy standards and earned the nickname "Siren In the Dark".