Ryuichi and Ryuji are twin boys who were adopted at birth by the Yoshie couple. Soon after, Mrs. Yoshie gave birth to a little girl that they named Misa. Mr. Yoshie was the owner of a small shipping company and the five of them lived comfortably together as a family. When the twins turned 15, the company went through a hostile takeover from the shipping magnate Kirishima Genpei. The Yoshie couple tried to fight the takeover but failed and ended up committing suicide over the huge debts they had accumulated in the process. Ryuichi and Ryuji made a pact to avenge the deaths of their adopted parents. Fast forward to seven years later. Ryuichi had faked his death and underwent plastic surgery to change his looks to join the underworld. On the other hand, Ryuji joined the Ministry of Land, Infrastructure, Transport and Tourism and works in the division that oversees the shipping industry. Only Ryuji is aware of the fact that Ryuichi is still alive, and the two of them slowly commence their plan to revenge on Kirishima.
