Every day, Naoto Hachiouji is teased relentlessly by Hayase Nagatoro, a first year student he meets one day in the library while working on his manga. After reading his story and seeing his awkward demeanor, she decides from that moment on to toy with him, even calling him Senpai in lieu of using his real name. At first, Nagatoro's relentless antics are more bothersome than anything and leave him feeling embarrassed, as he is forced to cater to her whims. However, as they spend more time together, a strange sort of friendship develops between them, and Naoto finds that life with Nagatoro can even be fun. But one thing's for sure: his days will never be dull again.

Naota Nandaba is an ordinary sixth grader living in a city where nothing amazing ever seems to happen. After his brother Tasuku leaves town to play baseball in America, Naota takes it upon himself to look after everything Tasuku left behind—from his top bunk bed to his ex-girlfriend Mamimi Samejima, who hasn't stopped clinging to Naota since Tasuku left. Little does Naota know, however, that his mundane existence is on the verge of being changed forever: enter Haruko Haruhara, a Vespa-riding, bass guitar-wielding, pink-haired psychopath whose first encounter with Naota leaves him with tire tracks on his back and a giant horn on his head. Though all he wants is some peace and quiet, when Haruko takes up residence at his parents' home, Naota finds himself dragged into the heart of the greatest battle for supremacy that Earth—and quite possibly the entire universe—has ever seen.

It has been 10 years since Heaven's Gate appeared in South America and Hell's Gate appeared in Japan, veiling the once familiar night sky with an oppressive skyscape. Their purposes unknown, these Gates are spaces in which the very laws of physics are ignored. With the appearance of the Gates emerged Contractors, who, in exchange for their humanity, are granted supernatural abilities. In the Japanese city surrounding Hell's Gate, Section 4 Chief Misaki Kirihara finds herself at odds with an infamous Contractor codenamed Hei. Called Black Reaper in the underground world, Hei, like his associates, undertakes missions for the mysterious and ruthless Syndicate while slowly peeling back the dark layers covering a nefarious plot that threatens the very existence of Contractors. From the mind of Tensai Okamura comes a sci-fi thriller taking the form of a subtle exposé on a war in which political positions and justice have no sway—a war waged exclusively in the shadows.

The Seven Deadly Sins, along with Elizabeth Liones and Hawk, have won the Kingdom of Leones back from the Holy Knights. At long last, it's their time to indulge in the peaceful lives they fought for. From inedible meat pies, overdue battles, unexpected stalkers, and the butterflies of first love, the Sins are accompanied by their friends in their carefree, fun-filled time together. However, the calm is broken with the premonition of a new threat, bringing upon the signs of Holy War and threatening to shatter the peace of the Sins' easygoing days.