God accidentally kills fifteen-year-old Touya Mochizuki with a stray bolt of lightning. Deeply apologetic, the deity offers to reincarnate Touya into a
fantasy world, granting him a single wish: to bring his smartphone along, which God modifies to function in the new realm while remaining connected to Earth’s power grid. God also vastly enhances Touya’s physical attributes, magical capacity, and grants him an affinity for all magic attributes.Awakening in this vibrant, medieval-fantasy realm, Touya quickly saves two twin sisters, Elze and Linze Silhoueska, from ruffians using magic. Grateful, the girls guide him through guild registration, where Touya discovers his overwhelming power. He easily defeats dangerous monsters and solves minor regional conflicts, quickly gaining notoriety and wealth. As his journey continues, Touya’s kindness, chivalry, and immense capability naturally attract a growing circle of companions. He rescues and recruits Yumina Urnea Belfast, the royal princess of Belfast; Yae Kokonoe, a fierce samurai girl from a distant eastern nation; Sheol, a magical artisan; and Leen, a millennia-old fairy professor.Despite the relaxed, slice-of-life atmosphere surrounding Touya's daily exploits, overarching threats drive the narrative forward. Touya uncovers the terrifying menace of the "Frase," monolithic, crystal-like monsters from another dimension that threaten the world's existence. He also investigates the mysterious ruins left behind by the ancient "Babylonians," a
civilization that vanished centuries ago. By solving riddles and using his unique smartphone abilities, Touya locates and connects the floating islands of Babylon, granting him access to devastating ancient weapons, infinite knowledge, and the brilliant homunculus creators who designed them.Touya’s motivations shift from simply surviving his new life to actively protecting his expanding family and the entire world from impending annihilation. He forms deep romantic bonds with the heroines, eventually becoming engaged to multiple girls with the blessing of the King of Belfast. As political tensions rise between neighboring human kingdoms, Touya plays a crucial mediating role, utilizing modern strategies and magic to outmaneuver corrupt nobles and treacherous factions.The dramatic climax of his initial adventures involves Touya leading a coalition of nations against early incursions of the Frase. Utilizing his smartphone to coordinate defenses, summoning legendary beasts, and wielding supreme magic alongside his devoted fiances, Touya pushes back the otherworldly invasion. He establishes the independent Brunhild Dukedom, becoming a sovereign ruler dedicated to peace and preparing humanity for the inevitable return of the full Frase army. Touya embraces his destiny as a powerful protector, balancing the responsibilities of statesmanship, romance, and continuous magical mastery in a world that owes its salvation to a boy and his divine smartphone.