An Unknown World

Yui Tachibana, a book loving, independent high school girl, had nightmares ever since she turned thirteen. Her life was the same ever since, until the day when a new student, Haruhiko Aoshi, came to her school. Many good things happened to Yui, but something bad happened the next day. Yui spotted a kreatur, a dangerous monster that could not be seen by humans. Yui and her friends were attacked, but they were saved by three people who were kreatur slayers. Since Yui could mysteriously see the kreaturs, Yui and her friends were to become a kreatur slayer whether they like it or not.