魔王の俺が奴隷エルフを嫁にしたんだが、どう愛でればいい? An_Archdemon's_Dilemma:_How_to_Love_Your_Elf_Bride まどめ 魔奴愛
The original title roughly means, "As the Demon King, what would be the right way to love my elf slave bride?"
Official English Title: "An Archdemon's Dilemma: How to Love Your Elf Bride"

A light novel by Fuminori Teshima and illustrated by C O M T A.

The sorcerer Zagan spends his fortune to buy [[Nephelia]] ("Nephy"), a white-haired elven slave (rumored to make good magic sacrifices), after falling in love with her at first sight.  His dark magic terrifies her, as does the torture device-riddled abandoned castle he's been squatting in, convincing her that he's more interested in torturing her than love, especially since he's too antisocial to string together a sentence.  Also, The Church is convinced he's the flesh-reaping serial murdering sorcerer that targets virgins, and has sent holy knights to bring him to justice, led by a [s]side romantic interest[/s] sword maiden he once saved.

Hilarity ensues.

Not to be confused with [[Isekai Maou To Shoukan Shoujo no Dorei Majutsu]], the OTHER light novel about a Maou with a busty elf slave waifu.
maou no ore ga dorei elf wo yome ni shitanda ga dou medereba ii?