Both the light novel and manga series were licensed by American publisher J-Novel Club for an English-language publication.

The story of the series follows Yuki, who was suddenly summoned in a fantasy world as a demon lord tied to his own dungeon.

When Iluna was kidnapped by said slavers some days later, Yuki and Lefisios ilfitrate the headquarters in attempt to rescue their newest family member.

Meanwhile, unbeknownst to his father, prince Lute who is eager to seize the lands of Yuki for its riches and sends the heroine Nell to the territory to get rid of the demon lord.

Happily Ever After with Monster Girls in My Dungeon on the user-generated online platform Shōsetsuka ni Narō on October 1, 2016.

The first printed volume in tankōbon format was published on January 9, 2019, under their Dragon Comics Age imprint.

[6] The childlike character design of Lefisios and Iluna was criticised negatively, while Yuki not being attracted sexually to them was pointed out positively.

The translator was praised for the effective usage of modern language in a story setting in a medieval fantasy world while the plot was criticized for not giving any information about Yuki's life before he was summoned as a demon lord.