Tsukasa Hashimoto

Kou Nishito, a graduate student suffering from insomnia, and Yoiko Ichijo, who has been unable to sleep due to loneliness since becoming independent, are discovered to be "compatible" individuals with a highly compatible sleep gene, "Nemunoki." They begin a cohabitation experiment to achieve stable sleep. Though hesitant, they fall asleep in the same bed, and drift into a deep sleep they haven't experienced in years... The feeling of having someone beside you. The curtain rises on a strange and heartwarming story of two awkward people. (Source: Kadokawa, translated)

A mysterious rift opened in the sky. From it, poured forth monsters known as the Abyss; corrupting the world and pushing it to the brink of destruction. After losing those he loved to the Abyss, in the depths of his rage, Ray awakens an unknown power. It is a demonic factor inherited from his father— the power of the Demon King, capable of erasing even the Abyss itself. As the only one in the world to awaken the ability to seal the rift, Ray is presented with two paths for saving humanity: Become the Demon King and rule over the demon race, or stand as humanity’s hero and annihilate the Abyss. On his journey to close the rift, Ray is forced to confront the ultimate choice…!