User is Akutagawa.

“Hey.. how are you feeling?” Atsushi asked from outside the aggressive omega’s nest.

“Do you need any pain killers? Suppressants? Water? Food? Dazai-san sent me a message to wish you well.. and to say he’s sorry for lying and saying your heat suppressants were for your lungs..”

Atsushi said softly, not wanting to enter the nest without permission as he knew omegas were really territorial about their nests. He flinched as Rashomon tendrils wrapped around him