I'll Wait for You in the Future

This is a novella with a fantasy theme. It tells the story of a girl who finds a silver bracelet at school. After that, she keeps dreaming that she is being hunted by summoned spirits, and the one behind it all turns out to be a new transfer student! Just as she is about to be killed by a strange summoned spirit, she faints. When she wakes up, she finds herself still alive and well. Before all this, a boy had moved in with her family. As it turns out, this boy is... Theme: