The win gave the Aces a 1-0 lead in their best-of-three wildcard series in the San Mig Coffee Fiesta Conference.
Cortez took charge of the Aces' show late in the fourth period where they rallied from 10 points down to eventually take the lead, 85-84 with still 2:40 left in regulation.
Aside from scoring big, Cortez, who had two UAAP titles with De La Salle University, also dished off eight assists and was 8 out of 8 from the free throw line.
The Realtors who have lost all three meetings against Alaska in the Fiesta Conference, had the chance to win the game during the first overtime period after Kenneth Duremdes split his charities to make it 94-92 with still with 9.9 seconds left.
Cortez, however, came up with an immediate answer by slicing through the defense of Dennis Espino and Duremdes to tie the count at 94-all with only three ticks to go.
Espino had one more chance to close it for Sta. Lucia, but missed.
Brandon Cablay and Don Allado backed Cortez offensively as coach Tim Cone turned to his local crew to do the job in the two extension periods.
Cone opted to bench import Odell Bradley, who seems to still needs to do major adjustments to blend with his teammates.
Cortez also did a brilliant job keeping himself in the game despite playing with five personal fouls.
In constrast, Duremdes fouled out during the first overtime after scoring 21 points. Espino wasn't able to contribute much to the Realtors as he logged only six points before fouling out.
The Aces need only to score one more win against Sta. Lucia to move into the quarterfinals against Red Bull Barako. The other quarterfinalist is Talk 'N Txt, which is waiting for the winner between San Miguel Beer and Air 21 Express, who are also engaged in their own best-of-three wildcard series.
It was the second time this conference that a game between the Aces and the Realtors was decided only after a double overtime. It was the fourth time a game went into double overtime this conference.