^ I'm leaving out quite a bit but essentially: Lingzi was engaged to a man she suspected was doing evil things (kidnapping and the like) and thought that were she to marry him she'd put the Enchanted Lands in even more danger. To stop him she sought Komari's help but because she didn't think Komari would just say yes normally her assistant hypnotised Komari to fall in love with Lingzi. This then lead to the battle between Komari and Shidou being a "Matrimonial War", the winner of which would "earn the right" to marry Lingzi. Komari won the war and then Lingzi's father instantly took them to a wedding ceremony and even though the ceremony was cut short they're still married on paper.
Also, Lingzi's father abdicated his title as Tianzi to Komari and Komari being Lingzi's spouse kinda helped with that so there's nothing Vill or Sakuna can really do about it anymore.