Aleksandar Cavric scored a first-half hat-trick for Kashima, title winners in 2018, to allow the J-League champions to dish out a lesson to Mark Milligan's side at Kashima Stadium in the eastern league phase opener.
"I think we started the game very well, we pressed them almost all the time so it was quite intense in the first half," said Cavric, who scored in the 11th and 16th minutes to give Kashima early control.
"We didn't give them much time to think so that's why we were able to create many chances."
James Delianov's own goal in the 19th minute left Newcastle with a challenging task that became insurmountable when Homare Tokuda hit the fourth in the 40th minute and Cavric completed his hat-trick two minutes later.
Tokuda and Kyosuke Tagawa scored in the second half for Kashima before Patrick Wood netted a 79th minute consolation for the visitors.
Shanghai Port saw Prince Ampen score three times in 15 minutes at the end of the first half to put Kevin Muscat's side in control of their meeting with hosts Ratchaburi with Wu Lei adding a fourth in the 51st minute.
The introduction of Njiva Rakotoharimalala gave Ratchaburi hope, the Madagascar international scoring a late hat-trick but the Chinese Super League side held on to secure their first win in the competition since November 2024.
Takashi Usami scored twice as Japan's Gamba Osaka won 4-1 against tournament debutants Cong An Ha Noi from Vietnam while Victor Bobsin's long-range curling strike earned Daejeon Citizen a 1-0 victory over Kyoto Sanga.
Neil Etheridge made an 87th minute penalty save from Bergson da Silva to ensure 10-man Buriram United secured a 1-1 draw with hosts Johor Darul Ta'zim and Beijing Guoan handed South Korea's Pohang Steelers a 3-1 defeat at Workers Stadium.
The top eight finishers in the 16-team eastern league phase will advance to the knockout rounds, with the tournament's quarter-finals, semi-finals and final to be played in Saudi Arabia in April and May.