Boku no Sekai wo Mamoru Hito

is a Japanese light novel series written by Nagaru Tanigawa, with illustrations by Akifumi Orizawa. The series began publication on November 10, 2005 by ASCII Media Works under their Dengeki Bunko publishing imprint.

Synopsis
"Did you finally come back?"

As soon as he came home, the boy was greeted by a strange girl. "Isn't it late?" The girl lifted her eyebrows. The name seems to be "Tsumon Ayaba Tsumugi". But how should I read it? Eventually she declared to the boy. "I will be your guardian from now on." The boys who had no reason to be guarded were just confused ... Since then, she says, "attackers" have come one after another! A mysterious magician holding an eerie stuffed animal to a little girl who self-destructs 5 meters away. The «world» that was commonplace for boys is breaking down !?