The visitors, who finished third last season, took control as Yosuke Kashiwagi opened the scoring in the 37th minute and Genki Haraguchi added a second six minutes into the second half.
Koji Morisaki replied for the champions four minutes later, but the Diamonds hung on for victory.
Yokohama F. Marinos are sitting pretty at the top of the table after the opening matches, having come from behind to beat newly-promoted Shonan Bellmare 4-2.
Yokohama took the lead through Shunsuke Nakamura five minutes before the break, but Tiago Quirino equalised within seconds and then gave last season's Division Two runners-up a shock lead with a 61st minute strike.
Marcos Marquinhos levelled it up once more in the 74th minute and late goals from Manabu Saito and Marquinhos again, this time from the penalty spot, sealed it for Yokohama.
Last year's runners-up Vegalta Sendai were held to a 1-1 draw at home to Division 2 champions Vantforet Kofu, who levelled through Hugo Almeida midway through the second half after Kodai Watanabe put Vegalta ahead.
Two late goals saw Shimizu S-Pulse come from 2-0 down to draw 2-2 at Omiya Ardija.
Two breakthroughs in 10 minutes - a Calvin Jong-a-Pin own goal and a Takuya Aoki strike - had the hosts in control by the 65th minute, but Hideki Ishige got one back in the 74th minute and Kenta Uchida completed the comeback 10 minutes later.
FC Tokyo came from behind to win 2-1 at Oita Trinita. The hosts led through Jung Choi's 17th minute goal but Kazuma Watanabe had Tokyo level with nine minutes and Aria Jasuru Hasegawa's 57th minute goal proved the winner.
Yoichiro Kakitani's goal two minutes from time gave Cerezo Osaka a 1-0 win over Albirex Niigata.
Hiroki Yamada scored in the 71st minute to give Jubilo Iwata a 1-1 draw away to Nagoya Grampus Eight after they had gifted the hosts a 36th minute lead through Byung-Kuk Cho's own goal.
Yohei Toyoda struck a 71st minute equaliser for Sagan Tosu, cancelling out Yuya Osako's first-half goal in a 1-1 draw with Kashima Antlers.