Now I'm a Demon Lord! Happily Ever After with Monster Girls in My Dungeon (Manga) Volume 7 by Ryuyu

Reborn in another world, Yuki should be enjoying his laid-back second life with his new family, especially after making headway in his relationship with Lefi. But an evil dragon suddenly arrives, intent on making the Supreme Dragon his mate on his quest for world domination. Of course, Yuki refuses to take that lying down, and thus begins their fierce battle to the death! The fate of the world hangs in the balance, but Yuki’s only concerned about protecting his wife’s honor. What’s in store for the not-so-wicked demon lord?!

Also includes cozy episodes featuring Yuki and the gang’s daily lives (when not in crisis mode). Science experiments, new pets, and even a visitor from the demon world?! There’s no downtime for this hero who thinks he’s a villain!