Gyakuten Ippatsuman, the sixth installment of the Time Bokan series, is set in a 1990s‑era Osteandel City. The city hosts Time Lease, a company that rents almost everything imaginable, including powerful robots. Proud of being the top-ranked billionaire company worldwide for ten consecutive years, Time Lease enjoys a reputation for success. Across town, a rival leasing firm, Skull Lease, employs the notorious villain trio as its senior executives. While they publicly claim to aim only to tarnish Time Lease's reputation and usurp its position as the leading enterprise, their true objective is to establish a foothold for world domination. The conflict ignites when a Time Lease transport robot is attacked by the villains.