A Chuuya that isn't actually Chuuya? Some sort of poet and sort of annoying. He could definitely be more annoying, however, so Akutagawa tolerates him and doesn't completely despite him.
Ugh, this guy... For some reason he has Dazai's respect and, at one point, thoroughly thwarted Akutagawa's attempts to murder him. Akutagawa utterly hated him for both of these reasons but, well... he died, and Akutagawa didn't. His rage has cooled considerably in the past few years.