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

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)