The Japanese trio of Reo Hatate, Daizen Maeda and Kyogo Furuhashi made their Champions League debuts on Tuesday as Celtic were beaten 3-0 at home by holders Real Madrid in Group F.
At Celtic Park, Hatate pulled the strings in their three-man midfield, while half-time substitute Daizen Maeda missed a huge chance before the Spanish giants put on a clinical show in front of goal with strikes from Vinicius Jr, Luka Modric and Eden Hazard.
Hatate's 20th-minute long-range volley was saved by Thibaut Courtois a minute before Celtic captain Callum McGregor saw an effort from the edge of the box cannon off the post as the home side more than matched the visitors in the first 45 minutes.
Maeda had a chance two minutes after coming on but failed to make proper contact on a cross from Josip Juranovic before Real, the defending European champions, took control.
Vinicius Jr. put them ahead in the 56th minute on a counter while Modric doubled their lead on the hour mark with a neat finish off the outside of his boot from inside the box.
Hatate went off in the 72nd minute with Furuhashi, taken off minutes into the Old Firm derby against Rangers on Saturday with a shoulder injury, coming on. But Hazard tapped in Dani Carvajal's header five minutes later to put the game to bed.
"That's the gap between us and Real," said Furuhashi, who did manage to threaten with a shot off his thigh that sailed just wide of the post in the latter stages.
Celtic manager Ange Postecoglou rued conceding first in a game in which his side showed plenty of promise.
"The first goal was always going to be pretty important on the night, and up until that point I thought we were well in the game," the former Yokohama F Marinos manager said on the Celtic website.
"If anything, we had the better opportunities but we didn't take them and those are the margins at this level."