She is more of a follower than a leader.
Shizu has brown eyes and brown shoulder length hair that she wears in short pigtails. She is usually seen wearing her school uniform.
She is seen in the very first chapter of the manga, being one of the girls to greet Sumire when she returns to the dorm after curfew. She ends up being used as one of the human shields by the virus Lucia is hunting at the school.
In Chapter 18 when she comes to visit Sumire with the other girls, we find out that they are all 14 years old, only a year younger than Lucia.