Template:Character infobox Kengo the Madman is a member of the anti-yakuza vigilante group known as The Reapers, whom Kazuma Kiryu faces off against during the Hitman sidestory in Yakuza 3.
Background
Kengo was once part of an unspecified Tojo Clan family. However, one night while he and his sworn brother were cutting across a Kamurocho back alley, they were attacked by a deranged stranger. The assailant murdered Kengo's oath brother, mutilating his body while he laughed maniacally. Kengo tried to stop the killer, but he was overpowered and sustained a serious head injury in the struggle. After he regained consciousness, he discovered that he couldn't stop laughing, even while staring at his friend's butchered body, likely as a result of the blow he took to the head.
Kengo's yakuza family came to believe that he was the one who'd killed his oath brother and thus he was expelled. Due to this error and the fact that he couldn't stop laughing, Kengo gained a reputation as a psychotic killer, even though he'd never killed anybody. After some time, Kengo was offered a job by the Reapers. Since he was still in a deluded state because of the psychological trauma and the head injury, Kengo agreed, despite never having killed anyone.
Yakuza 3
While Kiryu is visiting the Honest Living Association's offices in Okinawa, he is told about Kengo's presence nearby and he decides to try to question him about the Reapers.
Kiryu encounters the hitman in the empty lot under the Ryukyu train station, where he's chuckling to himself. Kiryu tries to talk him into coming willingly to the HLA but, in his deluded state, Kengo snaps at Kiryu and attacks him. Kiryu defeats Kengo easily but, surprisingly, during the fight Kengo took another blow to the head and has finally stopped laughing.
Now somewhat more sane, Kengo agrees to go to the HLA to see if they can help him with his mental problems. As a reward for getting Kengo to defect, Kiryu is paid 130,000 yen.