Mousou Kikou: Adolescence Avatar

Mousou Kikou: Adolescence Avatar (妄想奇行 Adolescence Avatar) is a manga series by Daisuke Moriyama. It was serialized in Dengeki Daioh Genesis.

Plot
Yazaki Yuuri, a transfer student, wants to be a popular high school kid. Also, despite how nerdy he knows it is, he's secretly working on writing a light novel. When strange things start happening around campus, an eccentric female student, Sakurabi Yukimi, explains to him that he has the power to unintentionally cause the creatures of his imagination to take physical form! Is it even possible for him to maintain his cool image while he's fighting the imaginary monsters from his formerly secret magic-girl light novel?