He's mine

Double black, which consisted of Osamu Dazai and Chuuya Nakahara, had been secretly married for the past four years. it was well known in yokohama and as well as the underground world, that port mafia and the detective agency are always at each other's throats, but unexpectedly, they formed an alliance for an important mission. Just what could be the threat that would require these two opposing forces to work together in order to defeat it?

(I do not own BSD💀 )