Ryoma is a former military man who gets to know the leader of a yakuza group and begins to work with them, helping them defend themselves against other yakuza gangs.

恥に生きるな、男で生きろ！蛮勇と腕力だけの暴れん坊が軍隊生活を皮切りに、幾度か悪徳やくざと対決しながら、遂に恩を受けた親分の組織を継いで大事業を成し遂げる勇壮男性編。