The 2013 finalists looked to be heading for a second straight defeat to Sanfrecce when Hwang Seok-Ho put the visitors 2-1 up in the 70th minute.
However, Sanfrecce were reduced to 10 men two minutes from the end of normal time as defender Hiroki Mizumoto was shown a second yellow card for an off-the-ball incident in the area.
Seoul defender Osmar's effort from the resulting penalty was saved, but the hosts were awarded a second spot-kick in the fourth minute of injury time, which substitute Rafael Costa converted after Kazuhiko Chiba had committed a similar offence to Mizumoto.
That result allowed Australia's Central Coast Mariners to move to the top of Group F with a 1-0 win over Beijing Guoan, defender Marcel Seip scoring the only goal of the game after Liam Reddy had saved a Zhang Xizhe penalty.
However, Western Sydney Wanderers could not continue the theme of Australian success, a deflected Kengo Nakamura effort and Ryota Oshima's thunderbolt giving Kawasaki Frontale a 2-1 victory.
Guizhou Renhe claimed their first win of the competition in Group H's other game, beating leaders Ulsan 3-1.
