The Mythical Hero's Otherworld Chronicles

Hiro Oguro is abruptly pulled from modern-day Japan into the realm of Aletia, only to realize this world is far from unfamiliar. A millennium ago, he walked these lands as Mars, the fabled Hero King who dominated battlefields, toppled nations, and forged the vast Grantzian Empire. Yet he willingly surrendered every memory of that hard-earned supremacy to reclaim his ordinary life on Earth. Now, thrust back into a world shaped by his ancient deeds, he finds his enduring legacy teetering on the brink of ruin. The empire he built groans under the grip of a warmongering ruler, while power-hungry royals scheme for the throne and rival nations mass their armies at the borders. When a fateful meeting with Princess Elizabeth von Grantz pulls Hiro into a ruthless contest for imperial succession, he realizes neutrality is no longer an option. To protect the realm from total collapse, he must resurrect the mantle of the War God and confront the impossible question of whether he can truly live up to his own myth when Aletia needs him most.