Eko to Toru to Kutatsu no Jikan.

is the first volume of the Eko to Toru light novel series, written by Yanagida Kokuri and Illustrated by MACCO. It was released under the Dengeki Bunko Imprint in February 2013.

Synopsis
A cynical school mystery woven by a human model talking with a twisted girl. My name is [Eko]. I have no friends. However, [Toru], who is in the department room of the chemistry department to which he belongs, is a noisy "speaking human model" and persistently insists that he is a friend. [Eko], who was isolated from the class due to an incident that occurred half a year ago, gets acquainted with [Tooru], a human model who speaks in the department room of the chemistry department that he joined one day. [Eco] is a human model who speaks with a voice as if she passed through a voice changer. [Toru] A girl student suddenly starts a strange club activity in which you gently hesitate. An incident of spontaneous combustion occurs and [Eko] is suspected as a suspect in the incident ... "Oh my god, I was involved in troublesome things." The 19th Dengeki Novel Grand Prize  winning work!

(source: Bookwalker JP - Translated)