Ancient tales recount the exploits of four legendary heroes—armed with sword, spear, bow, and shield—guarding the realm from relentless disasters. As the world's destiny hangs in the balance, Melromarc's kingdom beckons these heroes; in present-day Japan, the summons finds unexpected recipients, whisking them away to a mystical realm. Emerging in Melromarc, Naofumi Iwatani, an otaku, earns the moniker of 'Shield Hero,' deemed feeble for his lack of attack prowess and seeming inexperience. As the heroes diverge on their individual paths, Naofumi finds solace solely in the company of the enchanting Princess Malty Melromarc. Yet, her swift betrayal, theft of his possessions, and false accusations shatter his trust. Branded a criminal and cast off by society, Naofumi harbors a festering grudge, departing alone on a quest for retribution against those who betrayed him.