Uta wo Wasureta Genjuu to Ikenie no Hanayome

In Isabella's village, an ancient ritual is being carried out to ward off a poor harvest. The ritual involves offering a bride to a mythical beast, and her best friend, who is about to be married, is chosen to play the role. Unable to bear the sight, Isabella becomes the bride's substitute and is taken to the cave where the mythical beast lives. When Isabella comes face to face with the mythical beast, she asks him to use his song to bring fertility to the village, but... https://www.cmoa.jp/title/303658/