Donketsu Gaiden is a spin-off manga set in the same gritty yakuza underworld as the parent series Donketsu, but it shifts the focus to the younger years of key supporting characters. The story follows Kaneda, Masa-roquette (the man who will later become the feared veteran known as Rokemasa), and Chakashin as they navigate the harsh ranks of the Gachiringumi syndicate in the streets of Kyushu. During this formative period, the three are still climbing the ladder, each driven by ambition, survival instinct, or a raw desire for respect. The narrative depicts their early violent exploits, the alliances and rivalries they forge, and the brutal lessons that shape their reputations within the organization. As they rise through the lower tiers of the gang hierarchy, the manga explores themes of loyalty, pride, and the unforgiving nature of the modern yakuza world. The setting remains the seedy, cigarette-smoke-filled back alleys of Kokura, and the tone is rough and grounded, offering a closer look at how men at the bottom of the system become hardened by the life they chose.