Wanko-Kei Osananajimi no Kishi ga, Otto ni narimashite

Alan, a crybaby childhood friend who is like a younger brother, and Tina, who has been like a loving older sister. Alan grows up to become a knight in the royal capital and rises to the rank of captain of the Kingsguard. One day, however, Alan returns to the village in a great hurry after his success in defeating the demons, and says, "I'm so lonely, I'm going to die!" By the time Tina had taken in the situation, she was living as a "wife" in a mansion in the royal capital. They had not even been lovers for a long time, and now they are told to slowly become husband and wife...and then mysterious honeymoon planner shows up.