Japan, bidding for a third Asian Men's Volleyball Championship in a row at this year's event in Iran, got their campaign off to a formidable start with a convincing win against Hong Kong China, as unseeded India shocked second seeds Kazakhstan.
The defending champions overcame their opposition 25-21, 25-15, 25-11 in their opening Pool B game at the 12,000-seater Azadi Sports Complex in Tehran.
The top seeds are also the record winners of the competition, having triumphed nine times before this 20th running of the event.
India took a two-game lead over the side that earned silver behind Japan last time round, by 31-29 and 25-14.
Kazakhstan rallied to win the next two 30-28, 25-18, but India won the decider 15-9 to fill second place in Pool C behind China, the sixth seeds and three-time champions, who beat Oman 25-17, 22-25, 25-18, 25-16.
Shortly afterwards, the hosts, who won the 2011 and 2013 tournaments and have taken gold at the last two Asian Games, got off to an ideal start as they defeated Sri Lanka 25-15, 25-17, 25-23 in their opening Pool A match.
In the earlier Pool A match, eighth seeds Australia survived a scare against ninth-seeds Qatar to come through 25-23, 25-21, 23-25, 18-25, 15-10.
In the other Pool B match, Chinese Taipei earned a 3-1 win over Thailand, 25-16, 23-25, 25-16, 25-21.
The two Pool D matches went to form as South Korea and Indonesia, seeded third and fourth, earned respective wins over Kuwait and Pakistan.
Indonesia beat Kuwait 22-25, 25-20, 25-17, 25-18 and South Korea defeated Pakistan 3-0.
The top two teams from each pool will reach the quarter-finals and also qualify for the Asian Olympic Qualification Tournament for Tokyo 2020.
The final is scheduled for September 21.