In The Titan's Bride (Kyojinzoku no Hanayome), high schooler Kōichi Mizuki is summoned to the giant world of Eustil, where Prince Caius Lao Bistail makes him his husband to fulfill a prophecy. The series, created by ITKZ, features the couple navigating their new life together and is available as both a manga and an animated series.
You can purchase volumes on eBay or explore character details on the Yaoi Wiki . Kyojinzoku no Hanayome