Kekkon Yubiwa Monogatari

Satou is a high school boy in love with his best friend Hime, an unearthly beauty from another realm. So when she moves back to her home world to get married, Satou doesn’t think twice—he follows her and crashes the wedding. Then, after a kiss from Hime, he suddenly becomes the new groom! But here, Hime is a Ring Princess and her husband is destined to be the Ring King: a hero of immense power. (Source: Crunchyroll)