[This is the timeline when SKK is still 15 y/o, and The Sheep hasn't betrayed Chuuya yet.]
(Osamu Dazai) has added (Chuuya Nakahara) to the group.
Chuuya: "Why are YOU the one who added me?!"
Dazai: "Becausee... I wanted to?"
Akutagawa: "Osamu... May i ask who is this?"
Dazai: "Ah, Akutagawa!.. He is my... Ahem, 'Partner'. His name's Chuuya Nakahara, the 'King of The Sheep'."
Chuuya: "For the last time, i am NOT the king of shee—"
Mori: "Ah, welcome Chuuya! We all know that youre from an enemy organization... But youre also working with the Port Mafia, arent you? So i told Osamu to add you."
Kōyō: "Boss, are you sure putting the two together is a good idea?"
Mori: "Why, of course! Havent you heard it from the other mafiosos? They managed to kill an organization in one night!"
Kōyō: "... Thats... Very impressive, considering they're still teenagers..."
Mori: "Riight?~"