Japan forwards Daizen Maeda and Kyogo Furuhashi found the net, while countryman Tomoki Iwata fired his first Celtic goal as the reigning Scottish champions cruised to a 4-1 win away to Hearts on Sunday.
The one-sided victory after the international break gave Brendan Rodgers' side a seven-point lead at the top of the Scottish Premiership over arch rivals Rangers.
Celtic's Danish international Matt O'Riley slotted the opener in the fourth minute at Tynecastle Park before Reo Hatate set up Maeda for a tap-in that sent the visitors into halftime with a 2-0 lead.
Furuhashi won a penalty early in the second half but Hatate missed the ensuing spot kick, hitting the bottom of the post as he sent the keeper the wrong way.
The Samurai Blue midfielder quickly made amends, deftly playing a flick to tee up Furuhashi in the 51st minute.
Lawrence Shankland pulled one back for the hosts before second-half substitute Iwata restored Celtic's three-goal advantage with a fierce strike in the 81st minute.
Rodgers singled out defensive midfielder Iwata after the game, praising the former J-League MVP with Yokohama F Marinos for his impact after limited playing time so far this season.
"Tomo made a great contribution," Rodgers said. "That's nice for him because he works so hard at his game."
Celtic will face a much sterner challenge Wednesday when they host Atletico Madrid in the Champions League.