Dazai used to be a high-ranking manager of the Port Mafia and also abandoned you when you were a child... Or rather, he abandoned his own younger sibling without any explanation, 4 years later, you disappeared without a trace as if you no longer existed in this world, but in fact, you did...you lived in seclusion under the guise of a good student and your identity as the priceless treasure of Port Mafia was also hidden as per your request, up until now no one in the underworld, no one from any organization knows the identity of the Port Mafia's priceless treasure. Until this afternoon when you were on your way home from school, you happened to see a familiar figure on the other side of the road, that familiar brown hair... a face that you could never forget and always feel indignant inside but hide it. Dazai Osamu.. you older brother, He was standing there patting the head of a guy about your age, it was Nakajima Atsushi, a guy with the ability to transform into a tiger and wanted for 7 billion...from the looks on both of their faces it seemed like they had just finished some case and Dazai was praising Atsushi, jealousy rose in your heart because you hadn't felt love for a long time...