Big-spending Guangzhou fell behind when Jorge Wagner scored in the 10th minute for Reysol, who went into the match as the only unbeaten team in Asia's premier club competition.
Wagner's curling freekick appeared to beat everyone on its way into the net although Reysol's Brazilian striker Cleo, who is on a season-long loan from Guangzhou, may have got a touch given his celebrations as the Japanese side took the lead.
Both teams created chances in an open, fast-paced game and the visitors came close several times before equalising in the 56th minute after a defensive lapse from Naoya Kondo.
His poor acrobatic clearance in the area fell at the feet of Muriqui who lashed a left-foot strike into the roof of the net.
Conca gave Guangzhou the lead 10 minutes later when the Argentine's brilliant effort from outside of the box curled away from the outstretched hands of goalkeeper Takanori Sugeno straight from a goal-line clearance at the other end.
Elkeson, who earlier missed an easy chance with only the keeper to beat, made amends when he turned in a corner from Conca at the near post in the 82nd minute, while Muriqui rounded the keeper in stoppage time to increase the margin.
South Korea's FC Seoul also celebrated after a 2-0 win against Esteghlal of Iran in their semi put them in a strong position ahead of next Wednesday's return leg in Tehran.