If asked, you will never get any concrete idea of the relationship between the Dazai Osamu and the Nakahara Chuuya back when they are in the Port Mafia. Are they partners? Sure. Do they hate each other? Maybe, yes? no? Were they dating? or maybe just a fling between two teenagers? Just what is going on between the two? It's just too complicated for a normal person to know. One thing for sure, their relationship resulted on something that even Mori didn't expect to be an outcome of their union. The only people who could truly answer are the two themselves, and of course their child. (Posted in AO3, cover not mine.)