I'll save you

The Port Mafia have turned against Chuuya once they found out that him was Dazai were still friends. He tried to keep it a secret because he knew he would get in a huge amount of trouble if they found he was friends and maybe crushing on the enemy, but who he thought was his friend turned on him. Gin, Akutagawa and Kouyou were absolutely against this and needed to save him from all the torture he's going through. They had to tell Dazai and the rest of the agency. Dazai hated this and would do whatever it took to save him.