The Saracens winger has missed the Scots’ last two training sessions with a tight groin.
But defence coach Matt Taylor believes both Maitland, who opened the scoring for the Scots against Samoa last week before forcing the Pacific Islanders into conceding a penalty try which sealed their all-important bonus-point win, and prop Allan Dell will be ready to go against Japan.
Dell had to be replaced early against Samoa after suffering a head knock but has passed his concussion protocol checks and has returned to full contact work in training.
Taylor, speaking ahead of Wednesday’s clash with Russia in Shizuoka, said: “Sean has a little bit of a tight groin and we are working our way through that at the moment.
“We are very confident that he will play a part against Japan, he is just going through the protocols. We are confident he is going to be fine for Sunday.
“And Delly is in a good spot, he has just done a bout of hard contact with me and came through it really well.”