A world where it has been established that people routinely swing between slightly different parallel worlds... Koyomi Takasaki, who lives with his mother following his parents' divorce, enrolls in a local university prep school. Due to the atmosphere concentrated on studies and his social awkwardness, Koyomi is unable to make friends. One day, he is suddenly approached by his classmate Kazune Takigawa, who tells him that she has travelled from the 85th world where she and Koyomi are lovers.

For high school student Tanaka, the act of being listless is a way of life. Known for his inattentiveness and ability to fall asleep anywhere, Tanaka prays that each day will be as uneventful as the last, seeking to preserve his lazy lifestyle however he can by avoiding situations that require him to exert himself. Along with his dependable friend Oota who helps him with tasks he is unable to accomplish, the lethargic teenager constantly deals with events that prevent him from experiencing the quiet and peaceful days he longs for. [Written by MAL Rewrite]

Kouta has girl troubles of the supernatural sort. For some reason, he keeps attracting the attention (and affections) of animal spirits! Having spent most of his life in the country, Kouta is understandably nervous when he moves in with his grandma to attend a high school in the big city. He hoped to make a good impression, but having Chizuru, a beautiful fox spirit, hanging off his arm didn't seem to be the sort of image he wanted to have. She's not alone in her love for Kouta, either. Nozomu, a wolf spirit, as well as other youkai have their sights set on the hapless country boy.

The Sacred Kingdom has enjoyed a great many years without war thanks to a colossal wall constructed after a historic tragedy. They understand best how fragile peace can be. When the terrible demon Jaldabaoth takes to the field at the head of a united army of monstrous tribes, the Sacred Kingdom's leaders know their defenses are not enough. With the very existence of the country at stake, the pious have no choice but to seek help wherever they can get it, even if it means breaking taboo and parlaying with the undead king of the Nation of Darkness!