Gekkou centers on the unusual dynamic between a cynical boy and a flawless girl. The cynical boy is Nonomiya, who spends his days in boredom, seeking refuge from his dull existence in his imagination. One fateful day, he comes across the notebook of the much-rumored beauty Youko Tsukimori, which has been left neglected on the ground. Protruding from it is a scrap of paper bearing the unexpected title "Murder Recipe." His interest piqued, he immediately pockets it, only to discover that the promising recipe contains nothing but scenarios that may or may not lead to deadly accidents, hardly worthy of being called a plan. When he tentatively asks her about it the next day, she claims to have lost nothing. But then her father dies. An accident...