The Fifth Fist of the "Eight Fists League". He lives for the music and composes using his battles as inspiration for the melodies. Later he becomes Niijima's personal guard and a part of Shinpaku Alliance.

Hibiki Kugenin or Siegfried as he is referred to as was the Fifth Fist of Ragnarok. He is also called "the immortal composer" due to the fact that he composes music by using his battles as inspiration for his melodies. He has a tendency to hum or sing classical music during his fights and his attacks are named after different music scores and compositions. Like his namesake, he appears invincible, always getting back on his feet after taking a severe beating. This is actually due to his fighting style which uses counters and dodging an opponent's attack by the slightest margin. As such, he usually falls down on his own to fool his opponents. He is later defeated by Kenichi after being hit by a powerful punch Kenichi created himself. After their battle, he goes on a journey to find himself. Niijima later convinces him to join the Shinpaku Alliance in Battle 110, where he acts as the Alliance's combat leader, but mostly as Niijima's personal guard. In Battle 130 he can fight of Kensei's anesthic just by will power. A job he takes very seriously threatening even his own team mates if they go against Nijima who he calls his "dear demon king". He tends to only dodge attackers until Nijima orders him to attack and even feels pride if he was able to help Nijima in anyway, even when Nijima used his unconscious body as a human shield.
He is named after Sigurd, a hero in Norse mythology.