Yokohama F. Marinos, crowned J. League champions for the second year in a row on Saturday, became the latest high-profile victims in the Emperor's Cup on Wednesday after a shock 2-1 defeat to amateur league side Thespa Kusatsu in the fifth round.
But Urawa Reds put aside the disappointment of missing out on their first J. League championship title, after losing to Yokohama in a penalty shootout, with a 3-0 win over Shonan Bellmare to advance to the quarterfinals.
In Sendai, Thespa, which recently gained approval to join the J. League, took a shock lead through Daisuke Miyakawa after 30 minutes only for Daisuke Oku to level for under-strength F. Marinos six minutes from time.
But Japan Football League outfit Thespa, which stunned Cerezo Osaka in the previous round, pulled off another giant-killing act when Mitsumasa Yoda grabbed a "golden goal" in the 12th minute of extra time.
In Okayama, Urawa were missing top scorer Emerson, suspended after being sent off in Saturday's final, but Tatsuya Tanaka helped himself to a double to put Urawa on the way to victory.
Athens Olympian Tanaka scored in the 11th and 30th minutes before Makoto Hasebe sealed the win in the 85th minute.
Urawa's reward is a chance to avenge its penalty shootout defeat to FC Tokyo in the Nabisco Cup final in the next round. Thespa will face Tokyo Verdy.