Van Opstal rematched Harut Grigorian at War of the Ring in Amsterdam, Netherlands on February 2, 2011, losing by unanimous decision but he soon made a successful return to Japan where he would go on to have a string of wins over some of the nation's top middleweights and earn the moniker of "the Japanese Killer". At Shoot Boxing 2011: Act 3 on June 5, 2011, he stopped former boxer Satoru Suzuki with low kicks in round two.Shoot Boxing 2011 Act 3: Toby Imada Victorious, Rena Kubota Falls He then beat Mohammed Aouragh by decision at Muay Thai Mania 4 in Rijswijk, Netherlands on October 23, 2011Ismael Londt Continues Path of Demolition: Knocks Out Mourad Bouzidi before ending the year with a third straight win with a unanimous decision over Akihiro Gono at Shooto the Shoot 2011 on November 6, 2011.Shoot the Shooto/Shooto the Shoot Results: Souwer Gets Revenge, "Lion" and Bovy Score Upsets
