The Ultimate Humanoid Decisive Battle Weapon

Hundreds of years ago, giant monsters, the natural enemies of mankind, suddenly appeared on the continent. Facing the crisis of extinction on the continent, the remaining humans fled in all directions. People built cities with huge walls on the mainland and jokingly called them "corrals." In order to resist monster attacks, humans launched a project called the "Ultimate Humanoid Decisive Weapon" to build giant humanoid bodies powered by magic or steam to effectively fight back against invading giant monsters. An ungraduated college student traveled to this turbulent continent and became the third member of the "Laboratory" workshop-Arthur. How can this "outsider" with detailed science find his own way in this era where magic and steam civilization complement each other and electrical technology has sprouted.