The second-youngest of the four Hokuto brothers, Jagi was also the least skilled of them. He used a shotgun to dispense with most of his victims. Enraged at Kenshiro being chosen successor, he attacked him. Kenshiro defended himself and was preparing to finish Jagi with the Hokuto Hachimon Kyuudan (Eighth Agony, Ninth Break) technique, but with Jagi being his stepbrother Kenshiro could not bring himself to kill him. 

Despite this, Jagi's head became disfigured from Kenshiro's first attack. Utilizing his own Hokuto Shin Ken techniques, Jagi was able to counteract any further effects of the attack, and would later appear with metal implants to protect the swelling on his head.  The reason for this is that he appears to have a self conscious personality about his appearance and suffers from an inferiority complex. With even more hatred for Kenshiro, Jagi convinced Shin into taking Yulia from Ken. 

He professed to Shin that Kenshiro was unworthy of a Nanto woman and that only Shin could protect her. Jagi then donned a helmet to hide his hideous face and put seven scars on his chest. He then impersonated Ken and did horrible atrocities in Ken's name. During this period Jagi killed Rei's parents and kidnapped Airi, selling her into slavery. He also appropriated Nanto Sei Ken, however his Nanto Jarō Geki technique was so inferior that Kenshiro remarked on its slowness and that it was an insult to Shin's Nanto Sei Ken . Jagi was eventually hunted down and killed by Kenshiro, who remarked that a gruesome death befitted him.