The year is Showa 74 (1999 A.D.) and the world has been through much turmoil. The streets are littered with destitute buildings, crime, and also Sex☆Machines... mechanical humans that can be used as motorcycles by thrusting a penis inside of them. These Sex☆Machines have been in use since the olden days, however, when criminals began riding them, the police had to adapt, and began to use them as well. One of these officers is Suzuka Yoshimura, a rookie cop who doesn't play by the rules aided by the help of her Sex☆Machine "Ace". She recently heard of an exhibition that will show off a so-called "Legendary Sex☆Machine". What type of Sex☆Machine is it, and what is its goal?

A oneshot story about Kenshiro's sifu Ryuken and also the other adoptive brothers. Elaborates on how he chose the Hokuto Shinken successor and the events related to it.