I was summoned to another world where I got a rare "adults only" skill! Let the fun begin!

Summoned to a fantastical realm with the sacred duty of defeating the Demon Lord, the protagonist is bestowed with an impossibly overpowered SSR-tier ability known as [Alter World 18+]. This extraordinary skill grants him the power to duplicate any target’s abilities, but only under one highly specific condition: he must successfully “conquer” them. Should his efforts fail or circumstances turn dire, the skill provides an ultimate safety net, allowing him to rewind time back to the very beginning and attempt his approach again without limit. Operating much like a deeply immersive adult dating simulation, the mechanics of this power quickly shift the hero's priorities. The requirement to conquer individuals to absorb their strengths transforms his holy quest into something far more indulgent. Rather than focusing solely on martial preparation, he begins navigating complex romantic encounters to build his arsenal. Using the urgent mission to save the world as a convenient cover, the protagonist embarks on a relentless and unapologetic campaign. What starts as a traditional heroic journey rapidly evolves into a dedicated pursuit of assembling the ultimate harem, blending high-stakes fantasy adventure with shameless romantic ambition.