Within a mercenary guild, 14-year-old orphan Theo Asper is considered the weakest link and often shunned by his peers. Desperate to enhance his abilities, he stumbles upon the knowledge of a ritual that can summon a wish-fulfilling devil. Despite his initial goal of seeking power, Theo's heart takes an unexpected turn when he conjures Helvi, a benevolent devil whose sight captivates him. Entranced by Helvi's grace, Theo abandons his original wish and impulsively proposes marriage instead. Enchanted by Theo's sincerity and purity, Helvi agrees to his proposal. Despite numerous obstacles posed by foes and creatures, Helvi's immense power effortlessly safeguards their bond, paving the way for a blissful and harmonious life as newlyweds.