South Korean giants Ulsan Hyundai had already made the cut as guaranteed group winners, leaving FC Tokyo and Shanghai Shenhua scrapping for second place with both teams on seven points from five matches.
But Shanghai Shenhua fell to a crushing 4-1 defeat by Ulsan on Thursday to exit the tournament, while FC Tokyo's narrow win over Perth Glory helped them maintain their record of qualifying for the knockout phase every year since their continental debut in 2012.
Adailton was in the thick of the action in the very first minute at the Education City Stadium when he went for a spectacular bicycle kick off a cross from Takuya Uchida only to see the ball sail over the goalpost.
But he compensated for that miss in style seven minutes later with a brilliant 30-yard burst down the left flank, scoring with a curling shot past Perth goalkeeper Liam Reddy.
Two minutes later, Adailton found himself in a great position to strike again but his powerful effort from outside the penalty area saw Reddy producing a fine save.
Perth Glory took control of the match in the second half but could not get past the Tokyo defence, ending up at the bottom of the table with just one point from six matches.
FC Tokyo coach Kente Hasegawa said he always had confidence in his team's abilities.
"Today we are very happy about qualifying for the next round. Some players who didn't play much before played today and Adailton scored a very good goal," said Hasegawa.
"We tried to score more goals in the second half but also we knew the result of the other game (Ulsan were leading 2-0 against Shenhua at half time), so we were more comfortable."
Perth Glory's Cristian Ola said fatigue was a big factor for his team's poor show.
"Not happy with the result but happy with our boys' efforts and display considering it was their fifth game in a short space of time which is not something we are used to," said Ola.
"Fatigue was our biggest opponent today but congratulations to FC Tokyo."
Shanghai crash out
Shanghai Shenhua's defeat by Ulsan Hyundai meant they failed to make the last 16 for the first time since 2006.
Having booked their knockout berth earlier, Ulsan made several changes to their line-up but Park Jeong-in and Lee Sang-heon put them 2-0 ahead at the break.
Bjorn Johnsen then added a second-half brace as the Koreans recorded their fifth straight win.
"After we qualified for the round of 16, I expected a few players might lose concentration but all the players concentrated and played well," said Ulsan coach Kim Do-hoon.
"We had a lot of young players and they did their job. I asked them to play aggressively with combination play and high press, and they did it all very well."
Shanghai Shenhua's Choi Kang-hee said the Covid-19 pandemic meant they faced a number of difficulties in playing the competition.
"We understand it's a pandemic. It's a special time, and we have to play in this kind of way, but we hope in the future the tournament won't be played with such a tight fixture list."