Five participants have been announced for the eight-man tournament, which will send the winner against Takanori Gomi to crown the promotion's lightweight champion either on New Year's Eve or early next year.
Duane "Bang" Ludwig (16-8) enters the tournament looking to earn a rematch against Gomi, whom Ludwig lost to in March at "Sengoku" 1 by doctor stoppage.
Rodrigo Damm (8-1), who ended Jorge Masvidal's seven-fight win streak Sunday by TKO, aims to continue his own win streak, a nine-fight one, on August 24.
Kazunori Yokota (6-1-3), out of the GRABAKA team in Tokyo, turns to "Sengoku" after spending almost his entire career with DEEP.
PRIDE and G.C.M. veteran Eiji Mitsuoka (13-5-2) enters with a two-fight winning streak that began with a decision win over Joachim Hansen at Shooto "Back To Our Roots" 6. Mitsuoka fought at "Sengoku" 2 in May, submitting Kwang Hee Lee with a rear naked choke.
Also in the tournament is Pancrase mainstay Satoru Kitaoka (20-8-9), who won last month at "Sengoku" 2 by guillotine choke. The submission fighter has tapped out Carlos Condit, Paul Daley and Kurt Pellegrino.
"Sengoku" 4 will also feature Takanori Gomi against an opponent to be announced.