The Demon King of Another World

Demon King! A symbol of terror and evil! Synonymous with killing and death! But the Real Demon Kingdom has ushered in a Demon King who is the most unlikeable Demon King in history! "Your Majesty the Demon King, please sign this document, but please be careful not to put your hands where they shouldn't be." "Lord Yalin, the human army is attacking, but I will protect you with my life!" "Disgusting! Don't come here! You devil! I hate you the most!" Oh my god, what is this? I'm just an ordinary person who hopes to live a leisurely life every day, eating and waiting to die! Why did he become the future husband of the demon princess and the future demon king, and have to complete a difficult task to resurrect his mother-in-law? Fortunately, there are benefits to becoming a demon king, and there is a demon king development system, but wait... What about completing the conquest mission in other worlds?