Chuuya Nakahara is a werewolf. On days of the full moon, his hair gets thicker and fluffier, his nails and teeth sharpen, and his hearing and sight get better. On nights of the full moon, he shifts completely into a big wolf the size of a car and has no memory of it the next morning.

The first time Dazai got caught with Chuuya on a full moon was a little after they got married - the human had no idea what Chuuya was. Chuuya was scared for his husband, but came to the next morning to a safe Osamu. Turns out, his wolf form sees Dazai as a mate to protect. The human has stayed with Chuuya on full moons ever since.

Last full moon, there was an incident. Chuuya bit him. Dazai doesn't remember why exactly, but the result is what matters. Dazai hid it from Chuuya. He didn't want Chuuya to ban him from staying with him on a full moon, and it's not like the werewolf remembers it, so no harm, right?

Well, Dazai didn't know that getting bit by a werewolf turns you into a werewolf too was true. Chuuya told him once that most werewolf media was made up, so Dazai just assumed that was too and moved on, completely forgetting about the incident all together.

Now, a month later, Dazai feels weird and Chuuya can see something is very wrong. Dazai's been agitated all morning, his hair is thicker and fluffier than usual - he has sideburns now for fucks sake! - his eyes seem sensitive to the light, and his nails and teeth seem sharper. All symptoms Chuuya has on days of the full moon. Even his scent is different, smelling like... a fellow werewolf.

The sun was starting to set and the two were getting ready for the night - only an hour before the sounds of breaking bones as Chuuya transforms - and Dazai looking more and more rough as the moon approaches. Chuuya is starting to be suspicious now. What if... he bit Dazai.

He sighs as he finishes putting together the nest on their bed and crosses his arms as he looks at Dazai. "Hey, Osamu?" He asks to get the other's attention. "Did anything notable happen last full moon, maybe?"