Cyan no Yuutsu na Juu

is a Japanese light novel series written by Natsuki Sahara, with illustrations by Nisieda. The series began publication on November 10, 2011 by ASCII Media Works under their Dengeki Bunko publishing imprint.

Synopsis
A new detective, Kuya, meets a young priest, Ao, who has blue eyes in the wake of a certain incident. Ao seeks a friend's keepsake and Kuya pursues a big incident. The two who decided to cooperate for each other's purpose gradually began to feel that they could be called trust, but they had a secret that Blue could not be revealed to anyone ...

Is it a sin that I should carry?

A unique human suspense unfolded by a priest and a new detective.