The leader of the "Yamai Syndicate," a gang based in Honolulu City, Hawaii, appearing in Like a Dragon 8. Born August 19, 1973. Blood type O. Formerly a member of the Tabata Family, a direct subsidiary of the Tojo Clan. About 30 years before the main story, he fell in love with the patriarch Tabata's woman. Ultimately, he took the fall for the crime of killing his own patriarch and was excommunicated. After fleeing the country, he drifted to Hawaii. Even in tropical Hawaii, he is so sensitive to the cold that he wears a heavy coat, and he uses a crowbar in combat. He is always calm and collected, though he lets his guard down around the hostesses and members of his own territory. Furthermore, he holds a deep admiration for Kazuma Kiryu, who was once a legendary figure in the underworld, and shows an intense obsession with him until a certain point. He refers to Kiryu as "Kiryu-san." His first impression is poor due to his treatment of his subordinate, Eric Tomizawa, but contrary to his outward personality, he is well-respected by his organization and the local community. When Tomizawa tried to attack him, the hostesses (who seem to be older women, suggesting his preference) shielded him, saying, "If you lay a hand on Yamai, we won't forgive you." When he attempted to leave Hawaii, his subordinates tearfully saw him off, shouting, "We'll be waiting for you to come back, Boss!" He is a likable man whose soft-hearted nature occasionally peeks through, such as when he replies, "Don't die until I get back." However, he is the type to go all out when harassing someone he dislikes, regardless of profit or past grudges, showing a rather nasty side to his personality. Also, since he is technically no longer a yakuza, the group is the "Yamai Syndicate" rather than a "Yamai Family," but his members call him "Boss" (Oyaji) and refer to themselves as "family members" anyway. Initially, he corrected them every time, but since they never stopped calling him Boss, he eventually found it too troublesome and has recently left it alone. During his time in the Tabata Family, he was in love with the patriarch's wife, Yui Tabata, but she was also having secret meetings with the young head (wakagashira). At one point, Yui asked him to kill her husband, the patriarch, making it look like self-defense to hide her relationship with the young head. Yamai accepted the request with a sliver of hope that he might win Yui's heart. The plan went as expected, but immediately after the murder, Yui betrayed him, claiming he killed the patriarch and then tried to attack her, forcing Yamai to flee. While on the run, he became worried about Yui and went to check on her in secret, only to be devastated by the sight of her being intimate with the young head in public. This incident caused him to suffer from uncontrollable "chills" (the reason he wears a coat at all times). He subsequently fled to Hawaii to escape the Tabata Family and the police, where he formed the Yamai Syndicate with local Japanese-Americans.

Originally an honest taxi driver who had a pregnant girlfriend named Mary. However, Dwight Mendez, the leader of the Barracudas, framed the innocent Tomizawa for a crime they committed. The Barracudas had ties to the local police and judiciary, leaving Tomizawa powerless; he accepted the false charges and was sentenced to five years in prison. As a result, Mary suffered a miscarriage due to the stress and disappeared after visiting him once. He does not resent Mary for vanishing, saying instead that he was the one at fault for putting her through such hardship. However, he harbored a deep-seated hatred for the Barracudas, who ruined his life, killed his unborn child, and made Mary miserable. He went as far as obtaining a gun to seek revenge and found Dwight, but because he hesitated at the last moment despite being in a position to kill him at the cost of his own life, he became completely cynical and turned to a life of delinquency. The debt he incurred at that time was held by the Yamai Syndicate, and he has since been acting as one of Yamai's henchmen.