After Story 8 The Art Of Pleasing A Woman
Celeste lovingly held the back of William's head as the latter suckled her right breast, drinking her breast milk.
She only needed to wait for a month or two before her baby was born, but she felt uncomfortable whenever her breast milk would leak out from her breast and stain her clothes, creating wet patches whenever she was taking a stroll around the castle.
She was not the only one that had this problem, but William's other wives as well. Because of this, they had asked him to drink their milk to solve their problem.
They also did this to ensure that the Half-Elf wouldn't go and look for Ella for the same reason. For them, the Half-Elf could not drink anyone else's milk aside from their own.
"All of you really smell like milk," William commented after releasing Celeste's pink… from his mouth. "It's your turn, Erinys."