Dontores is the original Rumble King and one of the first generation Gravity Child. He is also an original member of the legendary Storm-Rider team, Sleeping Forest.
Yoshitsune, a brilliant strategist and occasional pervert, held the title of Rumble King and was the leader of the Kansai Storm Rider syndicate Tridents. Since Yoshitsune's death and the rumble regalia was given to Ikki by Benkei so it could help him in his mission of conquering Trophaeum tower, there's no one holding the title of the new Rumble King.