Astro King: Shoukan Yuusha dakedo Kakyuu Nintei sareta node Maid Harem wo Tsukurimasu!

Synopsis

After being transported to another world with all of his classmates, Yoshitsune was ordered to conquer the dungeon as a hero. While his peers were all reeled in and tamed by the offer of unlimited sex with the castle maids, Yoshitsune, a low-rank hero, devoted his cheat skills to getting more and more maid wives... (Source: Kill Time Communication, translated)