Dungeon de Tatakai Tsuzukete 20-nen no Doutei Yuusha, Chijou ni Modottara Danjohi 1:1000 no Sekai Datta

After descending into a dungeon to defeat the Demon King, the renowned hero Ryuuto spends two decades lost in its depths before finally emerging. The surface world has changed drastically: a curse has slashed the male population, and attitudes toward relationships have shifted along with it. Wherever he goes the women he meets are striking, and many compete for his attention, leading to repeated commotions he never intends to cause. Sensing the lingering influence of the Demon King behind the monsters now surfacing from the dungeon, Ryuuto throws himself back into combat. The series blends fantasy adventure with a comedic romantic-harem premise centered on its long-absent protagonist.