Kelvin awakens in a new world with no memory of his past, having traded his memories for powerful abilities during a mysterious summoning ritual. He quickly discovers that he possesses exceptional combat skills and the unique ability to summon and contract with powerful beings. Adopting the name "Kelvin," he embarks on a journey to uncover his lost memories while navigating the complexities of this unfamiliar world.

Accompanied by his first contracted summon, the warrior goddess Melfina, who serves as both a guide and a companion, Kelvin begins to explore the world and take on various quests. Melfina, bound to him through their contract, provides insight into his abilities and the world’s mechanics. Along the way, Kelvin forms a party with other skilled individuals, including the swordswoman Efil, a former slave he rescues and trains, and the mischievous demon girl Clotho, who joins him after a series of encounters.

The narrative unfolds as Kelvin and his companions undertake missions, battle formidable foes, and grow stronger through their experiences. The world is populated by adventurers, guilds, and mythical creatures, with a system of levels, skills, and magic that governs its inhabitants. Kelvin’s journey is driven by his desire to regain his memories, but it also explores themes of camaraderie, loyalty, and self-discovery as he builds relationships with his party members and confronts challenges that test their resolve.

As the story progresses, Kelvin’s past begins to surface in fragments, hinting at a deeper connection to the world and the summoning ritual that brought him there. The series balances action-packed battles with moments of character development, showcasing the growth of Kelvin and his companions as they face increasingly powerful adversaries and unravel the mysteries surrounding his existence. The interplay between Kelvin’s quest for identity and the bonds he forms with his allies forms the core of the narrative, set against the backdrop of a richly detailed fantasy world.