Chuuya is an alpha, like other homeless young alpha without parents, he too, never know how it's like to sleep in a mother's nest. If he has this weird intense yearning to be held by a mother, he'd sleep at an Omega's nest in the sheep. Every alpha in the sheep are like that too. They take a comfort from their own peer because there are no older alpha or omega in their little pack. In port mafia, it worse, because he doesn't know any omega that he can just ask to sleep on their nest because it's a private place. Kouyo is an alpha too. He loves it when she's holding him, but a comfort from an omega and their nest is different thing.
(I have no idea how to make him sleep on Mori's nest but he is. He's a way older omega so chuuya gets overwhelmed and crying because it feels so different. The nest is more comfortable and the scent is just more mature and feel more secure. Imagine if it's his mother's nest, must be more comfortable. No wonder orphans who had parents before they're being alone suffering from adjusting to life without their scent)