The beginning of Light Magic and the Hero, an otome RPG, unfolds fairly normally: the heroine, Alicia Ehnleit, meets her three love interests one after another and then inevitably comes face-to-face with the villainess. Yumiella Dolkness may be of noble descent, but her dark hair and rare dark-type magic—both associated with the Demon Lord—spark fear in anyone who sees her. When she is five years old, Yumiella regains memories of her previous life in modern Japan, also realizing that her fate is to become the hidden boss that appears after Alicia and her suitors defeat the Demon Lord. Yumiella refuses to live as the game dictates and, as she prefers the game's fantasy elements over its romance, she decides to cultivate her magical skills and level up in secret. However, everything falls apart on the day of the Royal Academy's entrance ceremony. Yumiella's powers are measured at level 99—something thought impossible even for the royal knights, let alone a 15-year-old girl. With the royal family requesting her help, and everyone else insisting that she prove her strength, Yumiella realizes that her dream of a quiet life is no longer an option.

As the commander of the Imperial Army's Third Legion, the Royal Empire's princess has led humanity to countless victories against the demonic Hellhorde. However, she has now been captured by the enemy and confined to the dungeons, with her sentient sword, Ex, as her only company. Due to her royal status, the princess knows invaluable secrets that would help the Hellhorde achieve dominance. To have her reveal all the information they need, the demons do not hesitate to subject the princess to the most vile forms of torture—that is, tempting her with delicious food, lasting friendships, adorable animals, and the most enjoyable experiences imaginable.

Spirits have always been attracted to Keitarou Gentouga due to his strong spiritual presence. A traumatic encounter with one had caused his right hand to be cursed, forcing him to wear a glove at all times. Now a college freshman, Keitarou is trying to live as normal a life as possible. With the encouragement of his childhood friend Eiko Houzuki, he becomes a private tutor. Since he is at the top of his intake class, his first client is the tutoring firm's most promising student, Yayoi Houzuki. To Keitarou's surprise, Yayoi is Eiko's cousin, and she possesses two pupils in each eye—allowing her to see into the spirit world and purposely seek vengeful spirits to exorcise. Ever since a car accident killed both her parents, Yayoi has been searching for the powerful spirit that kidnapped her mother's departed soul. Seeing that spirits are so attracted to Keitarou, she ropes him into helping her collect other evil spirits that will assist in her future fight. Although her quest is dangerous, Keitarou reluctantly decides to join her, even as each new spirit they meet has him questioning his resolve at every turn.

Despite returning victorious from a dangerous struggle, Kanata and his friends have, in a sense, lost a key ally, the amnesiac magus Noir. Having partially recovered her memory, Noir reverted back to her former personality: that of Mystere, who acts in a patronizing manner toward her master Kanata. However, Mystere remembers detecting a signal from Histoire, a mystical city, during her former life as an artificially intelligent magus. Meanwhile, Tokio disappears from Rock Town while hunting down the ghosts of his past; however, shocking revelations await the deeper his search goes. As Kanata, his childhood friend Ellie, and the magus diva Ciel set out for Histoire, a hostile organization named Ideal sends assassins after them. If Kanata wants to stand a chance at accomplishing his dream, he must uncover the unpleasant truth about Ideal—and some of his closest allies.