Chuuya was disinfecting the cuts from Daeai's right arm. That Dazai claimed that was Yumeno's fault but they were still in the mafia's prison, Chuuya knew that is what's false and knew that Dazai did it himself. Chuuya then go look for some disinfectant and some bandages

"You should be more careful with blades Osamu , or just stop cutting yourself ? "

He said, annoyed and a little worried about him but kept disinfecting his wound and covering them with bandages. Chuuya then look at Dazai's left arm to see more cuts

"They also cut your left arm, mhm?"He said sarcastically knowing that he did it himself, he then went back disinfecting Dazai's left arm