Oyama had his anticipated debut in PRIDE Fighting Championships in 2001 against feared Wanderlei Silva. In a fight of 30 seconds, Oyama met a spirited striking exchange, but he was overwhelmed and knocked out while he tried to avoid Silva. Shungo followed with a bout against famed Brazilian jiu-jitsu Wallid Ismail, but he underperformed again. The judoka met Ismail in his field of expertise by pulling guard early with a guillotine choke, which only allowed the Brazilian to pass guard, but Oyama escaped and contained Wallid until the second round. At the end, however, Ismail blocked a triangle choke attempt from Oyama and locked an arm triangle choke which Shungo refused to tap out to, rendering the Japanese unconscious. After the match, it was revealed that Oyama had suffered a retinal detachment.