Gamba Osaka began their Group E campaign in emphatic fashion with a 5-1 demolition of Melbourne Victory at Expo '70 Stadium.
The hosts went in front when Takahiro Futagawa delivered a corner that Takuya Takei converted unmarked in the middle of the box.
Adriano added a second from the spot two minutes later and Lee Keun-ho effectively put the encounter to rest with a third in the 11th minute as he stabbed home from close range.
Melbourne pulled a goal back when Archie Thompson was brought down and Kevin Muscat converted from the spot but Gamba restored their lead just after the hour mark when Adriano fed Takahrio Futagawa, who picked his spot. Kim Seung-yong then headed home a late fifth.
Hangzhou Greentwon enjoyed a successful start to Champions League life with a surprising 2-0 win over Nagoya Grampus in Group F at Yellow Dragon Stadium.
Substitute Ba Li proved the architect of the debutants opening victory, setting up Luis Ramirez to open the scoring shortly after the hour mark before wrapping up the points with a fine effort.
Group B saw Pakhtakor and Al Nassr share a 2-2 draw at Pakhtakor Stadium.
The hosts went in front on the stroke of half-time when Sherzod Karimov cut in from the right and beat goalkeeper Abdullah Al Anzi with a curling effort.
Bader Al Motwaa levelled from close range five minutes into the second period but Pakhtakor regained the ascendancy when Kakhi Makharadze nodded Karimov's free-kick back across goal and Dilshod Sharofetdinov headed in.
The Saudis equalised for a second time, though, when Mohammad Al Salhawi's cross was turned into his own net by Bojan Miladinovic.
In the group's other game, a late goal by Abdul Kaider Keta saw Al Sadd snatch a 1-1 draw at Esteghlal.
The hosts had gone in front midway through the first-half at the Azadi Stadium when Farhad Majidi was on hand to lash home following a poor clearing header.
However, Al Sadd levelled two minutes from the end when Nadir Belhadj's low cross was deflected and Keita headed home from inside the six-yard box.