When Lucien first met Oya he thought she would be an excellent mount, but now he considers her a beloved companion, and more than likely a wife when she gains a demi-human form.
So, he didn't really think much about using her as a mount anymore, but about her happiness.
He approached her and stroked her head. With Lucien being 1.84 meters tall and Oya as big as she is now. When stands up, she is now almost the same height as Lucien.
Oya now felt much bigger than Lucien, considering her entire size. She really likes the idea of carrying him on her back as she does with little Ko.
So she could defend him and she could smell his pleasant fragrance at the same time.
*Roar*
Oya roared in a low tone as she rubbed her head on Lucien's belly.