A dream team led by Sanshiro Higashi, who defeated Kinichi Akagi at the end of the previous work "1.2 Sanshiro 2" and was thought to have a bright future. However, in a match-fixing match offered by a major entertainment company, Sanshiro, who was supposed to lose, threw a single punch as a countermeasure early on in the match, knocking out his opponent . Even though he brought in the form of losing by receiving the Hishigi upside down cross, it ended in a big failure because the audience was mortified, and he was completely dried up from the martial arts world.

and years later. She is married to Shin Goto, and former dream team member Hotaru (maiden name: Honma), who runs a dry cleaning shop, realizes that Sanshiro is the missing homeless man she saw in the park. , astonished. The Gozu couple lamented that they had finally fallen to this point, but in fact, Sanshiro had opened a private office as a private detective, and his homeless appearance was a disguise to stake out an affair investigation .

Thus began a unique detective story in which Sanshiro Higashi, who was the strongest in the ring, used his animal-like knack and fighting ability to solve the case by force without using his brain.