She is the leader of the school girl rock band "Girls Dead Monster."
Masami Iwasawa is the lead singer and guitar player in the all girl rock band Girls Dead Monster. She writes all the songs and plays both acoustic and electric guitar. Girls Dead Monster are the "distraction squad" of the SSS. During missions they hold concerts to attract the attention of all the students in the school. Iwasawa is key to holding the attention of everyone as she is easily the most popular member.
In her pre-death life, Iwasawa lived with her parents who always argued; her father was an alcoholic. Once, when she tried to break up a fight between her parents, her father hit her on the head with a beer bottle. Not having her own room to retreat to, she hid in a corner of another room with her hands over her ears. She discovered a band called Sad Machine whose lead singer was in a similar family situation. Following the example of the singer, Iwasawa finds she can escape from her unhappy life by putting on headphones and listening to music. She finds an abandoned acoustic guitar and the rain. She picks it up and from then on, became a musician.
Iwasawa finished high school with high grades. Instead of going to college, she chooses to leave her parents house and move to the city to live by her music. She worked several part-time jobs--including one as a resutarant cook. She auditioned for a number of recording labels and performed many concerts. One day, she collapsed at work. At the hospital, she woke up unable to speak; she had suffered a brain stroke. Since she could no longer sing, she withered away.
In episode three, Girls Dead Monster's concert is interrupted by the school staff. A staff member attempts to take away her acoustic guitar (the same one she found abandoned), and Iwasawa becomes enraged. She yells at him not to touch it, breaks away from the teacher holding her, and grabs the guitar. She begins to play and sing a new song she wrote called "My Song." Her song captivates the audience, including Angel and the moe looking girl with pink hair--presumably her biggest fan. As she sings, Iwasawa reflects on her past life singing on the streets. She realizes singing and reaching people with her music is what she was born to do. In that moment, she vows to save someone through her music as she was saved by it.
Having realized her purpose and overcoming her regrets, Iwasawa disappears leaving only her guitar behind.