We know Oda was a close friend and a vital figure in Dazai's life. This is a proven truth. Chuuya is considerably different from Oda, and his connection with Dazai is likewise very different from Oda's. However, this does not rule out the possibility of Chuuya and Dazai becoming friends. They are both independent spirits who have no interest in following the crowd. If anything, it makes them even more likely to become friends because of this common ground they share. Here's how I see it: Chuuya is a loner who lives on his own terms. He has no interest in making friends with anyone so he wouldn't make any attempts to befriend others. At the same time, he is also extremely independent-minded who would never allow someone else to make his decisions for him. This combination of traits makes Chuuya and Dazai perfect partners in crime who share a love for breaking the rules. Now, as for their relationship after releasing Dazai from prison... Well, we don't know that yet! But given what we do know, it seems clear to me that if there was ever a chance for Chuuya and Dazai to become friends, this is exactly what happened.