Kyou Kara Ma no Tsuku Jiyuugyou!

Yuri Shibuya just can't catch a break. First, he had his head dunked in a toilet. Then he was transported to another world - where he finds himself king of the Mazoku's, a new race that expects him to lead them to war against all of humanity. And to top it all off, he's engaged - to a man!
(Source: Viz Media)