Kings are individuals who have been bestowed with incredible supernatural powers and granted the ability to recruit others into their clans. Protecting the lives and honor of their clansmen is an integral part of the Kings' duties. After a video depicting the heinous murder of a Red Clansman spreads virally, the unassuming student Yashiro Isana is accused of homicide. Now, a manhunt is underway for his head, bringing him into contact with the infamous Black Dog Kurou Yatogami—a skilled swordsman and martial artist determined to follow the wishes of his late master, the Seventh King. Meanwhile, the current Red King, Mikoto Suou, faces his own imminent demise as the search for Yashiro narrows. But during Yashiro's struggle to prove his innocence, a greater conspiracy is unraveling behind the scenes; clouds begin to appear in his memory, and close friends start to question his very existence. What began as a simple murder is now leading towards a full blown war between Kings with the very fate of the world at stake.

In the previous century, an unprecedented disaster known as the Invertia drastically reformed the world. The powers of existing nations declined significantly, paving the way for a conglomerate called the Integrated Empire Foundation to assume control. But more importantly, the Invertia led to the emergence of a new species of humans who are born with phenomenal physical capabilities—the Genestella. Its elite are hand-picked across the globe to attend the top six schools, and they duel amongst themselves in entertainment battles called Festas. Ayato Amagiri is a scholarship transfer student at the prestigious Seidoukan Academy, which has recently been suffering from declining performances. Through a series of events, he accidentally sees the popular Witch of Resplendent Flames, Julis-Alexia von Riessfeld, half-dressed! Enraged, Julis challenges him to a duel for intruding on her privacy. After said duel is voided by the student council president, Ayato reveals that he has no interest in Festas. Instead, he has enrolled in the academy to investigate the whereabouts of his missing elder sister. But when a more devious plot unravels, Ayato sets out to achieve victory, while being surrounded by some of the most talented Genestella on the planet.

Wishing to be independent, 16-year-old Maika Sakuranomiya is desperate to nail down a part-time job so that she can afford to study abroad. Unfortunately, her applications are constantly rejected due to the menacing look she unintentionally makes whenever she smiles, despite her otherwise cheerful disposition. After yet another failed interview, she chances upon Café Stile, a coffee shop where the servers interact with the customers while roleplaying distinctive characteristics. The Italian store manager, Dino, becomes infatuated with Maika's cuteness at first sight, and offers her a job as a waitress with a sadistic nature. Coupled with her inherent clumsiness, she successfully manages to serve a pair of masochistic customers in accordance with her new, ruthless persona. Alongside Kaho Hinata as the tsundere and Mafuyu Hoshikawa as the younger sister, Maika decides to make the most out of her unique quirk and cements her position in the cafe with merciless cruelty!

Running into your new stepsister in the bathroom is not the best way to make a good first impression, which Basara Toujou learns the hard way. When his father suddenly brings home two beautiful girls and introduces them as his new siblings, he has no choice but to accept into his family the Naruse sisters: busty redhead Mio and petite silver-haired Maria. But when these seemingly normal girls reveal themselves as demons—Mio the former Demon Lord's only daughter and Maria her trusted succubus servant—Basara is forced to reveal himself as a former member of a clan of Heroes, sworn enemies of the demons. However, having begun to care for his new sisters, Basara instead decides to protect them with his powers and forms a master-servant contract with Mio to keep watch over her. With the Heroes observing his every move and the constant threat of hostile demons, Basara has to do the impossible to protect his new family members. Moreover, the protector himself is hiding his own dark secret that still haunts him to this day...