The Asterisk War, Vol. 6 (light novel): The Triumphal Homecoming Battle — Yuu Miyazaki

Things are heating up in Liesentania!
At long last, the Phoenix is over, and New Year's Eve approaches. For winter vacations, Julis invites Ayato to visit her home in Lieseltania. As the king throws lavish parades and parties in their honor, Ayato comes to understand Julis's concerns for her country. To make matters worse, the king insists that Ayato and Julis marry each other! After the ruckus at their welcome party, another visitor makes her appearance--the Witch of Solitary Venom. She sets her sights on the pair, and Julis seems to know more than she's letting on...