本作主要描述了超越时空开展租赁事业的时光租赁社与邪恶租赁社之间展开的善玉同恶玉之间的攻防战以及职场人的悲哀，是时间飞船系列的第6部作品。为了打破老套的剧情本作在故事中张开了各种各样的伏线，可以说是系列中少有的独特风格作品。

Gyakuten! Ippatsuman is the sixth in the Time Bokan series. In the 1990s-era Osteandel City is the headquarters of Time Lease, a business that leases almost everything you could ask for including powerful robots. They are proud of themselves for being number one in the international ranking of billionaires, for the past ten consecutive years. Meanwhile there is another lease company in the same city called Skull Lease where the notorious villain trio work as top executives. Their ostensible object is to disgrace the credit of Time Lease and replace them as the leading enterprise. In fact, however, they have a scheme to secure a footing for world conquest. One day a transport robot of Time Lease is assaulted by the villain trio and it is time for Ippatsuman to get on the move to fight for justice.

どんな時代と場所にも客の望む商品を届けるタイムリース社。その配達員である放夢ランと弟分のハル坊、サポートロボットの2-3は、荷物を運んで様々な時代へタイムスリップする。だが、ライバル企業であるシャレコーベリース社の支社長ムンムンとその部下二人が、事あるごとにランたちの仕事を妨害。救援を求めるハル坊のピンチ通信を受け、正義のヒーロー・イッパツマンが時空を超えて駆け付ける。