Celtic lost 6-4 to J-League champions Yokohama F-Marinos on Wednesday as Brendan Rodgers began his second spell in charge of the Glasgow giants in a pre-season tour of Japan.
Daizen Maeda scored a first-half hat-trick for Celtic but Yokohama mounted a comeback after the break to spoil Rodgers's first game back after replacing Ange Postecoglou.
Rodgers won all seven available trophies during his first two-and-a-half-year stint at Celtic between 2016 and 2019.
He made a dramatic comeback to Parkhead after Postecoglou left for Tottenham after leading Celtic to the Scottish domestic treble last season.
Rodgers's side made a slow start in steamy Yokohama and goalkeeper Joe Hart gifted the Japanese side the lead with a howler in the fourth minute.
The former England number one dived at Anderson Lopes's feet to cut out a pass but lost control of the ball and left the striker with a clear path to stroke it into an empty net.
Celtic equalised just two minutes later after a lightning-fast break forward.
Reo Hatate found Liel Abada streaking forward on the right, and the Israeli carried it forward before squaring it for Maeda to finish off.
Abada was also the provider for Maeda's second goal, again finding the Japanese striker to tap home from close range in the 21st minute.
Celtic's lead only lasted two minutes before Kota Mizunuma blasted the ball past Hart for the equaliser.
Maeda, who extended his Celtic deal until 2027 earlier this month, completed his hat-trick with another deft finish in the 42nd minute.
But Lopes and Yuki Saneto struck for Yokohama in the second half before substitute Ryo Miyaichi hit two goals to turn the tables on Rodgers's side.
David Turnbull scored a consolation goal for Celtic with the last kick of the game.
Yokohama won the J-League under Postecoglou in 2019 before the Australian left to join Celtic two years later.
Yokohama won the league again last year under his successor Kevin Muscat, a former Postecoglou assistant.
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