The story picks up with Shido Reiji, a 17-year-old who has just returned to modern Japan after a two-year ordeal as a summoned hero in another world. He successfully defeated the Demon Lord and his forces, fulfilling his destiny. Reiji, now 19, retains the extraordinary combat prowess and immense magical power he gained from his summoning, capable of leveling mountains with a single spell. Despite his heroic feats, he finds himself grappling with his strong sense of justice, now amplified by his experiences.
His return is complicated by his relationships with two girls: Riona Saijo, his childhood friend, and Sylvia Granrion Martel, the former princess and saint who summoned him. Sylvia, a fifteen-year-old princess with immense magical talent, had summoned Reiji out of necessity, as she alone was not strong enough to defeat the Demon Lord. She developed deep romantic feelings for Reiji, who treated her as an equal. Her love is intense and possessive, leading her to follow him back to Japan, a decision that causes significant political issues for her kingdom but which she dismisses due to her overwhelming affection for Reiji.
Riona, a sharp and athletic girl, harbors her own unexpressed feelings for Reiji, often masking her affection with a tsundere attitude. Reiji's mother, Manami Shido, a cheerful and supportive woman, readily accepts Sylvia into their home and is amused by the romantic entanglements.
The narrative then delves into Reiji's past in the other world. Sylvia, as the summoned hero's educator, grew closer to Reiji. Their bond deepened as they fought together, and Sylvia's initial sense of duty evolved into profound love. The text highlights Sylvia's exceptional magical abilities, particularly in defense and healing, and her initial struggle to understand Reiji's casual demeanor.
A significant turning point occurs when Reiji, after defeating the Demon Lord, expresses his desire to return home. His companions, including the swordsman Gain Morlock, mage Sonya Rains, martial artist Alm Cohen, and cleric Katarina Cleynhal, bid him a tearful farewell. However, Sylvia, unable to bear the thought of separation, impulsively jumps into the magic circle with Reiji as he is being sent back.
Reiji and Sylvia find themselves in a forest in Japan. Reiji is initially frustrated by Sylvia's reckless actions, as her absence would cause chaos in her kingdom. Sylvia, however, justifies her actions by stating her duty as a saint was fulfilled and that her father and sister could manage the kingdom. Reiji, realizing Sylvia's stubbornness and the depth of her feelings for him, decides to deal with the situation. He notices his superhuman strength has persisted even after returning to Japan, a fact that surprises him.
They discover they are in a familiar location, Hiyama Greenery Park, which Reiji visited as a child. This fortunate turn of events allows Reiji to easily navigate back home. Sylvia, still dressed in her formal attire and heels, struggles with the terrain, leading to Reiji carrying her in a princess carry, a situation that causes her embarrassment and joy. Reiji reflects on the responsibility he now carries for Sylvia, acknowledging the immense trouble her impulsive act has caused. The chapters conclude with Reiji and Sylvia facing the immediate challenge of integrating into his world, with Reiji harboring a sense of guilt and responsibility towards Sylvia, while Sylvia experiences a mix of regret for disrupting Reiji's life and happiness at being able to share his world.
